The document presents a mathematical model for the static I-V characteristics of optically controlled GaAs MESFETs. The model characterizes photo-induced voltages, including internal and external photovoltages, as well as photoconductive current in the channel. It also considers the effects of deep level traps in the semi-insulating GaAs substrate, including the phenomenon of backgating, on the I-V characteristics. The model is developed analytically and expressions are derived for the I-V characteristics in both the linear and saturation regions of the MESFET under dark and illuminated conditions. Small-signal parameters of the GaAs MESFET are also derived based on the static I-V model under optical control conditions
Evaluation of phase-frequency instability when processing complex radar signals IJECEIAES
A new radar system for digital signal processing before detection is proposed. These are the guidelines for selecting an intermediate frequency for signal processing. The features of signal processing in the case of echo-signal selection by the features of the correlation properties of their complex bypass are described. This paper presents the study of ambiguity function (AF) when processing complex radar signals. In this work, the AF synthesis was performed considering non-determined components and the presence of phase-frequency instability. The received result enhances the potentials for distinguishing an incoherent radar signal. The numerical simulation results of received AF are presented. Considering fluctuation components in the complex AF, depending on the laws of the distribution of amplitude and frequency fluctuations and their parameters, allowed to get the gain in the width of the main lobe from the units to tens of times. Paper represents original analytical expressions for AF of radio-signals modulated by narrow band random processes with various distribution laws.
TCAD Based Analysis of Gate Leakage Current for High-k Gate Stack MOSFETIDES Editor
Scaling of metal-oxide-semiconductor transistors
to smaller dimensions has been a key driving force in the IC
industry. This work analysis the gate leakage current behavior
of nano scale MOSFET based on TCAD simulation. The
Sentaurus Simulator simulates the high-k gate stack structure
of N-MOSFET for analysis purpose. The impact of interfacial
oxide thickness on the gate tunneling current has been
investigated as a function of gate voltages for a given equivalent
oxide thickness (EOT) of 1.0 nm. It was reported in the results
that interfacial oxide thickness plays an important role in
reducing the gate leakage current. It is also observed that high-
k stack gated MOSFET exhibits improved performance in term
of Off current and DIBL
This document proposes a low-power full adder array-based multiplier circuit design using domino logic. It is based on the Wallace tree technique. The proposed circuit uses a clocked architecture that results in lower power dissipation and improved power-delay product compared to traditional designs. As a proof of concept, the authors implemented an 8x8 bit multiplier using multiple 4x4 bit multiplier blocks. Simulation results show the 8x8 multiplier design has an average power of 0.11108 microwatts when implemented using a 0.5um CMOS process at 5V supply voltage.
EVALUATION OF OPTICALLY ILLUMINATED MOSFET CHARACTERISTICS BY TCAD SIMULATIONVLSICS Design
In this paper we report effect of optical illumination on Silicon MOSFET. The MOSFET has been studied in
respect of current voltage, transconductance admittance and scattering parameters. Gain analysis of the
Silicon MOSFET is done in dark and under optical illumination. The device is fabricated using ATHENA™
process simulator and the device simulation is performed using ATLAS™ from SILVACO international.
The simulation results indicate potential of MOSFET as optically sensitive structure which can be used
for increase in data transmission/reception rates, reduction of interconnect delays, elimination of clock
skew, or as a photodetector for optoelectronic applications at low and radio frequency.
CNFET BASED BASIC GATES AND A NOVEL FULLADDER CELLVLSICS Design
In this paper two novel high performance designs for AND and OR basic gates and a novel Full-Adder Cell are presented. These designs are based on carbon nanotube technology. In order to compare the proposed designs with previous ones both MOSFET based and CNFET based circuits are selected. By the way the proposed designs have better performance in comparison with previous designs in terms of speed, power consumption and power-delay product (PDP).
A High Speed Pipelined Dynamic Circuit Implementation Using Modified TSPC Log...IDES Editor
This document presents a modified True Single Phase Clock (TSPC) logic design style to implement high-speed pipelined circuits with improved performance. The modified style reduces transistor count by 40-50% compared to the standard TSPC style by allowing logic functions to be implemented using either the N-block or P-block. A 3-bit pipelined adder was designed using the modified style and showed a 46-47% reduction in transistors and 50% reduction in clock cycles compared to the standard style. The modified style offers benefits like lower transistor count, reduced latency, increased throughput, and lower power consumption for pipelined circuits.
Iaetsd design and analysis of a novel low actuated voltageIaetsd Iaetsd
The document describes the design, analysis, fabrication process, and simulation of a novel low actuated voltage RF MEMS shunt capacitive switch. Key points:
1) A fixed-fixed flexure beam structure is used to provide a lower spring constant and reduce the actuation voltage below 4 volts.
2) The fabrication process involves 5 masks and materials like gold, silicon nitride deposited on a silicon substrate to form the switch.
3) Simulations show the switch has a low pull-in voltage of 3 volts and excellent RF characteristics with -0.12dB insertion loss and -43dB isolation at 28GHz.
This document describes a simplified SPICE behavioral model for a saturable core transformer. It consists of a saturable core modeled with parameters BSAT, RLOSS, LM, and BEXP that define the flux density versus magnetic field characteristics. An ideal transformer is also included with parameters N, RP, RS, and LP. The model focuses on reproducing hysteresis loop behavior in the operating area by allowing the user to shape the B-H curve by adjusting the core parameters. Examples are given of how varying each parameter affects the magnetic curve fitting.
Evaluation of phase-frequency instability when processing complex radar signals IJECEIAES
A new radar system for digital signal processing before detection is proposed. These are the guidelines for selecting an intermediate frequency for signal processing. The features of signal processing in the case of echo-signal selection by the features of the correlation properties of their complex bypass are described. This paper presents the study of ambiguity function (AF) when processing complex radar signals. In this work, the AF synthesis was performed considering non-determined components and the presence of phase-frequency instability. The received result enhances the potentials for distinguishing an incoherent radar signal. The numerical simulation results of received AF are presented. Considering fluctuation components in the complex AF, depending on the laws of the distribution of amplitude and frequency fluctuations and their parameters, allowed to get the gain in the width of the main lobe from the units to tens of times. Paper represents original analytical expressions for AF of radio-signals modulated by narrow band random processes with various distribution laws.
TCAD Based Analysis of Gate Leakage Current for High-k Gate Stack MOSFETIDES Editor
Scaling of metal-oxide-semiconductor transistors
to smaller dimensions has been a key driving force in the IC
industry. This work analysis the gate leakage current behavior
of nano scale MOSFET based on TCAD simulation. The
Sentaurus Simulator simulates the high-k gate stack structure
of N-MOSFET for analysis purpose. The impact of interfacial
oxide thickness on the gate tunneling current has been
investigated as a function of gate voltages for a given equivalent
oxide thickness (EOT) of 1.0 nm. It was reported in the results
that interfacial oxide thickness plays an important role in
reducing the gate leakage current. It is also observed that high-
k stack gated MOSFET exhibits improved performance in term
of Off current and DIBL
This document proposes a low-power full adder array-based multiplier circuit design using domino logic. It is based on the Wallace tree technique. The proposed circuit uses a clocked architecture that results in lower power dissipation and improved power-delay product compared to traditional designs. As a proof of concept, the authors implemented an 8x8 bit multiplier using multiple 4x4 bit multiplier blocks. Simulation results show the 8x8 multiplier design has an average power of 0.11108 microwatts when implemented using a 0.5um CMOS process at 5V supply voltage.
EVALUATION OF OPTICALLY ILLUMINATED MOSFET CHARACTERISTICS BY TCAD SIMULATIONVLSICS Design
In this paper we report effect of optical illumination on Silicon MOSFET. The MOSFET has been studied in
respect of current voltage, transconductance admittance and scattering parameters. Gain analysis of the
Silicon MOSFET is done in dark and under optical illumination. The device is fabricated using ATHENA™
process simulator and the device simulation is performed using ATLAS™ from SILVACO international.
The simulation results indicate potential of MOSFET as optically sensitive structure which can be used
for increase in data transmission/reception rates, reduction of interconnect delays, elimination of clock
skew, or as a photodetector for optoelectronic applications at low and radio frequency.
CNFET BASED BASIC GATES AND A NOVEL FULLADDER CELLVLSICS Design
In this paper two novel high performance designs for AND and OR basic gates and a novel Full-Adder Cell are presented. These designs are based on carbon nanotube technology. In order to compare the proposed designs with previous ones both MOSFET based and CNFET based circuits are selected. By the way the proposed designs have better performance in comparison with previous designs in terms of speed, power consumption and power-delay product (PDP).
A High Speed Pipelined Dynamic Circuit Implementation Using Modified TSPC Log...IDES Editor
This document presents a modified True Single Phase Clock (TSPC) logic design style to implement high-speed pipelined circuits with improved performance. The modified style reduces transistor count by 40-50% compared to the standard TSPC style by allowing logic functions to be implemented using either the N-block or P-block. A 3-bit pipelined adder was designed using the modified style and showed a 46-47% reduction in transistors and 50% reduction in clock cycles compared to the standard style. The modified style offers benefits like lower transistor count, reduced latency, increased throughput, and lower power consumption for pipelined circuits.
Iaetsd design and analysis of a novel low actuated voltageIaetsd Iaetsd
The document describes the design, analysis, fabrication process, and simulation of a novel low actuated voltage RF MEMS shunt capacitive switch. Key points:
1) A fixed-fixed flexure beam structure is used to provide a lower spring constant and reduce the actuation voltage below 4 volts.
2) The fabrication process involves 5 masks and materials like gold, silicon nitride deposited on a silicon substrate to form the switch.
3) Simulations show the switch has a low pull-in voltage of 3 volts and excellent RF characteristics with -0.12dB insertion loss and -43dB isolation at 28GHz.
This document describes a simplified SPICE behavioral model for a saturable core transformer. It consists of a saturable core modeled with parameters BSAT, RLOSS, LM, and BEXP that define the flux density versus magnetic field characteristics. An ideal transformer is also included with parameters N, RP, RS, and LP. The model focuses on reproducing hysteresis loop behavior in the operating area by allowing the user to shape the B-H curve by adjusting the core parameters. Examples are given of how varying each parameter affects the magnetic curve fitting.
Research Inventy : International Journal of Engineering and Science is publis...researchinventy
This document summarizes research on characterizing the electrical properties of AlGaN/GaN modulation-doped field-effect transistors (MODFETs). Key findings include:
- A threshold voltage of -3.87V, maximum saturation current of 122.748 mA, and transconductance values were achieved.
- Dependence of two-dimensional electron gas density at the interface on Al mole fraction and AlGaN barrier layer thickness was presented.
- A novel method for studying AlGaN/GaN interface properties by solving the Schrodinger and Poisson equations self-consistently using finite difference methods was developed. This allows calculating electron distributions, energy band structures, and other characteristics of
Analytic Estimation of Two-Dimensional Electron Gas Density and Current-Volta...IJECEIAES
This paper is mainly dedicated to understand the phenomena governing the formation of two-dimensional electron gas (2DEG) confined in the quantum well which hold the role of the channel in the high electron density transistors (HEMT) based on AlGaN / GaN heterojunction. The theory takes into account: the crystal structure, the spontaneous and piezoelectric polarization concept, the formation mechanism of two-dimensional electron gas at the AlGaN / GaN interface, the approximate resolution of the Poisson and Schrödinger equations to determine the density of Two-dimensional electron gas after the analytical formula of the current-voltage characteristic is established. Our study is also concerned with the dependence of the twodimensional electron gas density on the following technological parameters: Aluminum molare fraction, AlGaN layer thickness and AlGaN layer doping, In order to control the influence of these parameters on the device performance. Finally, the current-voltage characteristic which reflects the variation of the drain-source current as a function of the modulation of the gate voltage has been discussed.
LINEARITY AND ANALOG PERFORMANCE ANALYSIS OF DOUBLE GATE TUNNEL FET: EFFECT O...VLSICS Design
The linearity and analog performance of a Silicon Double Gate Tunnel Field Effect Transistor (DG-TFET) is investigated and the impact of elevated temperature on the device performance degradation has been studied. The impact on the device performance due to the rise in temperature and a gate stack (GS) architecture has also been investigated for the case of Silicon DG-MOSFET and a comparison with DGTFET is made. The parameters overning the analog performance and linearity have been studied, and high frequency simulations are carried out to determine the cut-off frequency of the device and its temperature dependence.
Frequency Dependent Characteristics of OGMOSFETidescitation
Miniaturization in length, lowering of power,
increase in package density and sensitivity to light of
MOSFET leads it as the potential candidate for RF application.
As device is expected to operate at RF, it is essential to observe
its frequency dependent characteristics at RF. In this paper
frequency dependent electro optical characteristics of
Optically Gated Metal Oxide Semiconductor Field Effect
Transistor (OGMOSFET) are investigated numerically.
Variation of drain current-voltage characteristics, gate
capacitance and transconductance of OGMOSFET, with
varying frequency, is reported. MOSFET having length of
0.35μm is selected for investigation, which is optically gated
with incident radiations of optical power of 0.25mW and
wavelength of 800nm. MATLAB is used as computational
platform to test and tune the results. Results show that
increase in modulating frequency of OGMOSFET decreases
drain current, gate capacitance, transconductance and output
conductance. This is due to decrease in life time of inversion
charges at very high frequencies. Operating bandwidth of the
device is up to 4GHz.
Effect of Series Resistance and Layer Thickness on PCE & Fill Factor in Pervo...IRJET Journal
This document summarizes a study that used electrical simulation software (GPVDM) to analyze the effects of series resistance and layer thickness on the power conversion efficiency (PCE) and fill factor (FF) of a perovskite solar cell with molybdenum trioxide (MoO3) and methyl ester (PC60bm) as the active layers. The simulation showed that adjusting the series resistance from 19.5 ohms to 5 ohms and optimizing the thicknesses of the MoO3 and PC60bm layers increased the PCE from 16.66% to 20.42% and improved the FF from 66.29% to 71.22%. In conclusion, properly selecting series resistance and
IJERA (International journal of Engineering Research and Applications) is International online, ... peer reviewed journal. For more detail or submit your article, please visit www.ijera.com
Comprehensive identification of sensitive and stable ISFET sensing layer high...IJECEIAES
The ISFET sensing membrane is in direct contact with the electrolyte solution, determining the starting sensitivity of these devices. A SiO2 gate dielectric shows a low response sensitivity and poor stability. This paper proposes a comprehensive identification of different high-k materials which can be used for this purpose, rather than SiO2. The Gouy-Chapman and Gouy-Chapman-Stern models were combined with the Site-binding model, based on surface potential sensitivity, to achieve the work objectives. Five materials, namely Al2O3, Ta2O5, Hfo2, Zro2 and SN2O3, which are commonly considered for micro-electronic applications, were compared. This study has identified that Ta2O5 have a high surface potential response at around 59mV/pH, and also exhibits high stability in different electrolyte concentrations. The models used have been validated with real experimental data, which achieved excellent agreement. The insights gained from this study may be of assistance to determine the suitability of different materials before progressing to expensive real ISFET fabrication.
This document summarizes the performance enhancement and characterization of a junctionless vertical slit field effect transistor (JLVeSFET). Key findings from simulations include:
1) The JLVeSFET shows an optimized subthreshold slope of 65mV/decade and OFF current of ~10-18A/μm for a 50nm radius device with a high-k dielectric.
2) Using a high-k dielectric (Si3N4) instead of SiO2 increases the Ion/Ioff ratio to ~1011 and reduces the subthreshold slope to 63mV/decade.
3) Increasing the gate doping concentration reduces the subthreshold slope slightly while increasing the Ion/
THE EFFECT OF INTERFACE MODIFICATION BY PEDOT: PSS ON THE HOLE MOBILITY OF TH...ijoejournal
The purpose of the work is to understand how to effect the interface PEDOT: PSS on the hole mobility of
the LEC device by Space Charge Limited Current (SCLC) approaches technique. PEDOT: PSS plays a
significant role in organic electronics device as interface modification, particularly on Light-emitting
electrochemical cells (LEC) due to fundamental structure of hole only device. This study analyses the hole
mobility of the device based on current-voltage characteristic approach at room temperature. It has been
observed that the PEDOT: PSS interface increases the hole mobility of the LEC device by a factor of 108
.
Geometric and process design of ultra-thin junctionless double gate vertical ...IJECEIAES
The junctionless MOSFET architectures appear to be attractive in realizing the Moore’s law prediction. In this paper, a comprehensive 2-D simulation on junctionless vertical double-gate MOSFET (JLDGVM) under geometric and process consideration was introduced in order to obtain excellent electrical characteristics. Geometrical designs such as channel length (Lch) and pillar thickness (Tp) were considered and the impact on the electrical performance was analyzed. The influence of doping concentration and metal gate work function (WF) were further investigated for achieving better performance. The results show that the shorter Lch can boost the drain current (ID) of n-JLDGVM and p-JLDGVM by approximately 68% and 70% respectively. The ID of the n-JLVDGM and p-JLVDGM could possibly boost up to 42% and 78% respectively as the Tp is scaled down from 11nm to 8nm. The channel doping (Nch) is also a critical parameter, affecting the electrical performance of both n-JLDGVM and p-JLDGVM in which 15% and 39% improvements are observed in their respective ID as the concentration level is increased from 1E18 to 9E18 atom/cm3. In addition, the adjustment of threshold voltage can be realized by varying the metal WF.
MODELING OF BUILT-IN POTENTIAL VARIATIONS OF CYLINDRICAL SURROUNDING GATE (CS...VLSICS Design
Due to aggressive scaling of MOSFETs the parasitic fringing field plays a major role in deciding its characteristics. These fringing fields are now not negligible and should be taken into account for deriving the MOSFET models. Due to this fringing field effect there are some charges induced in the source/drain extension regions which will change the potential barrier at the source-channel from its theoretical nominal values. In this paper an attempt has been made to model variation of built-in potential variation for a cylindrical surrounding gate MOSFET. The model has been verified to be working in good agreement with the variations of gate length and channel radius.
Temperature dependent electrical response of orange dye complex basedIAEME Publication
The document summarizes research on temperature-dependent electrical properties of Orange-Dye complex based Schottky diodes. Schottky diodes were fabricated from Orange-Dye and Vinyl-Ehtynyl-Trimehyl-Piperiodole complex deposited via spin coating. Current-voltage measurements showed the diodes followed the space charge limited current model. Analysis of this data determined how parameters like mobility, trap density, and threshold voltage varied with temperature, improving at higher temperatures. The study provided insight into charge transport within the organic semiconductor complex.
The document describes a simulation study comparing the RF and analog performance of different AlGaN/GaN MOSHEMT device structures. Single gate MOSHEMTs using SiO2, Al2O3, and HfO2 dielectrics were designed and simulated. Double gate and dielectric pocket double gate MOSHEMT structures were also simulated to improve performance. Simulation results showed the HfO2 dielectric pocket double gate MOSHEMT achieved the best performance with high drain current and transconductance, as well as high cutoff frequency over 1.95 THz, indicating suitability for analog and millimeter-wave applications.
The document summarizes research using spectroscopic ellipsometry to analyze Cu2ZnSnSe4 (CZTSe) thin films. Key findings include:
1) A refined model accounting for a ~220nm thick MoSe2 layer at the back contact improved the fit between measured and modeled ellipsometry data, allowing extraction of a more reliable CZTSe dielectric function.
2) Ellipsometry can detect the presence and thickness of secondary phase MoSe2 non-destructively.
3) Variations in dielectric functions between samples likely relate to composition variations and minor secondary phases.
This document summarizes a numerical simulation of a graded band gap GaAs/AlGaAs heterojunction solar cell performed with AMPS-1D modeling software. The simulation analyzed how a graded band gap region at the interface between the GaAs emitter and AlGaAs base layers affects solar cell performance. Results showed that a 0.14μm graded band gap region was needed to eliminate the conduction band spike and improve cell performance over an abrupt heterojunction. Photovoltaic parameters, including efficiency, of 31.1% were obtained for the cell with a graded interface, compared to 27.3% for an abrupt heterojunction cell.
The document discusses the design of an RF MEMS switch using COMSOL Multiphysics and Intellisuite simulation software. A cantilever beam switch structure is designed with dimensions and materials specified. Simulation results show the switch has a low actuation voltage of 4V, insertion loss of -8dB, and isolation of -40dB at 1.5GHz. To reduce the high resistance of a single switch, 10 switches are placed in parallel, lowering the effective resistance to 5.9 ohms. The switch performance is better at lower frequencies.
This document discusses the design and analysis of SRAM cells using tunneling field-effect transistors (TFETs) for ultralow-voltage operation. It analyzes the characteristics of TFET devices that impact SRAM performance, such as delayed saturation and broad crossover regions. Several published TFET SRAM cell designs are evaluated using technology computer-aided design simulations. The simulations show that the unidirectional conduction of TFETs degrades write stability. A novel 7-transistor driverless TFET SRAM cell is proposed to improve read, write, and hold stability through decoupled read paths and asymmetrical write-assist techniques.
TWO DIMENSIONAL MODELING OF NONUNIFORMLY DOPED MESFET UNDER ILLUMINATIONVLSICS Design
A two dimensional numerical model of an optically gated GaAs MESFET with non uniform channel doping has been developed. This is done to characterize the device as a photo detector. First photo induced voltage (Vop) at the Schottky gate is calculated for estimating the channel profile. Then Poisson’s equation for the device is solved numerically under dark and illumination condition. The paper aims at developing the MESFET 2-D model under illumination using Monte Carlo Finite Difference method. The results discuss about the optical potential developed in the device, variation of channel potential under different biasing and illumination and also about electric fields along X and Y directions. The Cgs under different illumination is also calculated. It has been observed from the results that the characteristics of the device are strongly influenced by the incident optical illumination.
Characterization of silicon tunnel field effect transistor based on charge pl...IJEECSIAES
The aim of the proposed paper is an analytical model and realization of the characteristics for tunnel field-effect transistor (TFET) based on charge plasma (CP). One of the most applications of the TFET device which operates based on CP technique is the biosensor. CP-TFET is to be used as an effective device to detect the uncharged molecules of the bio-sample solution. Charge plasma is one of some techniques that recently invited to induce charge carriers inside the devices. In this proposed paper we use a high work function in the source (ϕ=5.93 eV) to induce hole charges and we use a lower work function in drain (ϕ=3.90 eV) to induce electron charges. Many electrical characterizations in this paper are considered to study the performance of this device like a current drain (ID) versus voltage gate (Vgs), ION/IOFF ratio, threshold voltage (VT) transconductance (gm), and subthreshold swing (SS). The signification of this paper comes into view enhancement the performance of the device. Results show that high dielectric (K=12), oxide thickness (Tox=1 nm), channel length (Lch=42 nm), and higher work function for the gate (ϕ=4.5 eV) tend to best charge plasma silicon tunnel field-effect transistor characterization.
haracterization of silicon tunnel field effect transistor based on charge plasmanooriasukmaningtyas
The aim of the proposed paper is an analytical model and realization of the characteristics for tunnel field-effect transistor (TFET) based on charge plasma (CP). One of the most applications of the TFET device which operates based on CP technique is the biosensor. CP-TFET is to be used as an effective device to detect the uncharged molecules of the bio-sample solution. Charge plasma is one of some techniques that recently invited to induce charge carriers inside the devices. In this proposed paper we use a high work function in the source (ϕ=5.93 eV) to induce hole charges and we use a lower work function in drain (ϕ=3.90 eV) to induce electron charges. Many electrical characterizations in this paper are considered to study the performance of this device like a current drain (ID) versus voltage gate (Vgs), ION/IOFF ratio, threshold voltage (VT) transconductance (gm), and sub-threshold swing (SS). The signification of this paper comes into view enhancement the performance of the device. Results show that high dielectric (K=12), oxide thickness (Tox=1 nm), channel length (Lch=42 nm), and higher work function for the gate (ϕ=4.5 eV) tend to best charge plasma silicon tunnel field-effect transistor characterization.
A Novel Method for Prevention of Bandwidth Distributed Denial of Service AttacksIJERD Editor
Distributed Denial of Service (DDoS) Attacks became a massive threat to the Internet. Traditional
Architecture of internet is vulnerable to the attacks like DDoS. Attacker primarily acquire his army of Zombies,
then that army will be instructed by the Attacker that when to start an attack and on whom the attack should be
done. In this paper, different techniques which are used to perform DDoS Attacks, Tools that were used to
perform Attacks and Countermeasures in order to detect the attackers and eliminate the Bandwidth Distributed
Denial of Service attacks (B-DDoS) are reviewed. DDoS Attacks were done by using various Flooding
techniques which are used in DDoS attack.
The main purpose of this paper is to design an architecture which can reduce the Bandwidth
Distributed Denial of service Attack and make the victim site or server available for the normal users by
eliminating the zombie machines. Our Primary focus of this paper is to dispute how normal machines are
turning into zombies (Bots), how attack is been initiated, DDoS attack procedure and how an organization can
save their server from being a DDoS victim. In order to present this we implemented a simulated environment
with Cisco switches, Routers, Firewall, some virtual machines and some Attack tools to display a real DDoS
attack. By using Time scheduling, Resource Limiting, System log, Access Control List and some Modular
policy Framework we stopped the attack and identified the Attacker (Bot) machines
Hearing loss is one of the most common human impairments. It is estimated that by year 2015 more
than 700 million people will suffer mild deafness. Most can be helped by hearing aid devices depending on the
severity of their hearing loss. This paper describes the implementation and characterization details of a dual
channel transmitter front end (TFE) for digital hearing aid (DHA) applications that use novel micro
electromechanical- systems (MEMS) audio transducers and ultra-low power-scalable analog-to-digital
converters (ADCs), which enable a very-low form factor, energy-efficient implementation for next-generation
DHA. The contribution of the design is the implementation of the dual channel MEMS microphones and powerscalable
ADC system.
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Research Inventy : International Journal of Engineering and Science is publis...researchinventy
This document summarizes research on characterizing the electrical properties of AlGaN/GaN modulation-doped field-effect transistors (MODFETs). Key findings include:
- A threshold voltage of -3.87V, maximum saturation current of 122.748 mA, and transconductance values were achieved.
- Dependence of two-dimensional electron gas density at the interface on Al mole fraction and AlGaN barrier layer thickness was presented.
- A novel method for studying AlGaN/GaN interface properties by solving the Schrodinger and Poisson equations self-consistently using finite difference methods was developed. This allows calculating electron distributions, energy band structures, and other characteristics of
Analytic Estimation of Two-Dimensional Electron Gas Density and Current-Volta...IJECEIAES
This paper is mainly dedicated to understand the phenomena governing the formation of two-dimensional electron gas (2DEG) confined in the quantum well which hold the role of the channel in the high electron density transistors (HEMT) based on AlGaN / GaN heterojunction. The theory takes into account: the crystal structure, the spontaneous and piezoelectric polarization concept, the formation mechanism of two-dimensional electron gas at the AlGaN / GaN interface, the approximate resolution of the Poisson and Schrödinger equations to determine the density of Two-dimensional electron gas after the analytical formula of the current-voltage characteristic is established. Our study is also concerned with the dependence of the twodimensional electron gas density on the following technological parameters: Aluminum molare fraction, AlGaN layer thickness and AlGaN layer doping, In order to control the influence of these parameters on the device performance. Finally, the current-voltage characteristic which reflects the variation of the drain-source current as a function of the modulation of the gate voltage has been discussed.
LINEARITY AND ANALOG PERFORMANCE ANALYSIS OF DOUBLE GATE TUNNEL FET: EFFECT O...VLSICS Design
The linearity and analog performance of a Silicon Double Gate Tunnel Field Effect Transistor (DG-TFET) is investigated and the impact of elevated temperature on the device performance degradation has been studied. The impact on the device performance due to the rise in temperature and a gate stack (GS) architecture has also been investigated for the case of Silicon DG-MOSFET and a comparison with DGTFET is made. The parameters overning the analog performance and linearity have been studied, and high frequency simulations are carried out to determine the cut-off frequency of the device and its temperature dependence.
Frequency Dependent Characteristics of OGMOSFETidescitation
Miniaturization in length, lowering of power,
increase in package density and sensitivity to light of
MOSFET leads it as the potential candidate for RF application.
As device is expected to operate at RF, it is essential to observe
its frequency dependent characteristics at RF. In this paper
frequency dependent electro optical characteristics of
Optically Gated Metal Oxide Semiconductor Field Effect
Transistor (OGMOSFET) are investigated numerically.
Variation of drain current-voltage characteristics, gate
capacitance and transconductance of OGMOSFET, with
varying frequency, is reported. MOSFET having length of
0.35μm is selected for investigation, which is optically gated
with incident radiations of optical power of 0.25mW and
wavelength of 800nm. MATLAB is used as computational
platform to test and tune the results. Results show that
increase in modulating frequency of OGMOSFET decreases
drain current, gate capacitance, transconductance and output
conductance. This is due to decrease in life time of inversion
charges at very high frequencies. Operating bandwidth of the
device is up to 4GHz.
Effect of Series Resistance and Layer Thickness on PCE & Fill Factor in Pervo...IRJET Journal
This document summarizes a study that used electrical simulation software (GPVDM) to analyze the effects of series resistance and layer thickness on the power conversion efficiency (PCE) and fill factor (FF) of a perovskite solar cell with molybdenum trioxide (MoO3) and methyl ester (PC60bm) as the active layers. The simulation showed that adjusting the series resistance from 19.5 ohms to 5 ohms and optimizing the thicknesses of the MoO3 and PC60bm layers increased the PCE from 16.66% to 20.42% and improved the FF from 66.29% to 71.22%. In conclusion, properly selecting series resistance and
IJERA (International journal of Engineering Research and Applications) is International online, ... peer reviewed journal. For more detail or submit your article, please visit www.ijera.com
Comprehensive identification of sensitive and stable ISFET sensing layer high...IJECEIAES
The ISFET sensing membrane is in direct contact with the electrolyte solution, determining the starting sensitivity of these devices. A SiO2 gate dielectric shows a low response sensitivity and poor stability. This paper proposes a comprehensive identification of different high-k materials which can be used for this purpose, rather than SiO2. The Gouy-Chapman and Gouy-Chapman-Stern models were combined with the Site-binding model, based on surface potential sensitivity, to achieve the work objectives. Five materials, namely Al2O3, Ta2O5, Hfo2, Zro2 and SN2O3, which are commonly considered for micro-electronic applications, were compared. This study has identified that Ta2O5 have a high surface potential response at around 59mV/pH, and also exhibits high stability in different electrolyte concentrations. The models used have been validated with real experimental data, which achieved excellent agreement. The insights gained from this study may be of assistance to determine the suitability of different materials before progressing to expensive real ISFET fabrication.
This document summarizes the performance enhancement and characterization of a junctionless vertical slit field effect transistor (JLVeSFET). Key findings from simulations include:
1) The JLVeSFET shows an optimized subthreshold slope of 65mV/decade and OFF current of ~10-18A/μm for a 50nm radius device with a high-k dielectric.
2) Using a high-k dielectric (Si3N4) instead of SiO2 increases the Ion/Ioff ratio to ~1011 and reduces the subthreshold slope to 63mV/decade.
3) Increasing the gate doping concentration reduces the subthreshold slope slightly while increasing the Ion/
THE EFFECT OF INTERFACE MODIFICATION BY PEDOT: PSS ON THE HOLE MOBILITY OF TH...ijoejournal
The purpose of the work is to understand how to effect the interface PEDOT: PSS on the hole mobility of
the LEC device by Space Charge Limited Current (SCLC) approaches technique. PEDOT: PSS plays a
significant role in organic electronics device as interface modification, particularly on Light-emitting
electrochemical cells (LEC) due to fundamental structure of hole only device. This study analyses the hole
mobility of the device based on current-voltage characteristic approach at room temperature. It has been
observed that the PEDOT: PSS interface increases the hole mobility of the LEC device by a factor of 108
.
Geometric and process design of ultra-thin junctionless double gate vertical ...IJECEIAES
The junctionless MOSFET architectures appear to be attractive in realizing the Moore’s law prediction. In this paper, a comprehensive 2-D simulation on junctionless vertical double-gate MOSFET (JLDGVM) under geometric and process consideration was introduced in order to obtain excellent electrical characteristics. Geometrical designs such as channel length (Lch) and pillar thickness (Tp) were considered and the impact on the electrical performance was analyzed. The influence of doping concentration and metal gate work function (WF) were further investigated for achieving better performance. The results show that the shorter Lch can boost the drain current (ID) of n-JLDGVM and p-JLDGVM by approximately 68% and 70% respectively. The ID of the n-JLVDGM and p-JLVDGM could possibly boost up to 42% and 78% respectively as the Tp is scaled down from 11nm to 8nm. The channel doping (Nch) is also a critical parameter, affecting the electrical performance of both n-JLDGVM and p-JLDGVM in which 15% and 39% improvements are observed in their respective ID as the concentration level is increased from 1E18 to 9E18 atom/cm3. In addition, the adjustment of threshold voltage can be realized by varying the metal WF.
MODELING OF BUILT-IN POTENTIAL VARIATIONS OF CYLINDRICAL SURROUNDING GATE (CS...VLSICS Design
Due to aggressive scaling of MOSFETs the parasitic fringing field plays a major role in deciding its characteristics. These fringing fields are now not negligible and should be taken into account for deriving the MOSFET models. Due to this fringing field effect there are some charges induced in the source/drain extension regions which will change the potential barrier at the source-channel from its theoretical nominal values. In this paper an attempt has been made to model variation of built-in potential variation for a cylindrical surrounding gate MOSFET. The model has been verified to be working in good agreement with the variations of gate length and channel radius.
Temperature dependent electrical response of orange dye complex basedIAEME Publication
The document summarizes research on temperature-dependent electrical properties of Orange-Dye complex based Schottky diodes. Schottky diodes were fabricated from Orange-Dye and Vinyl-Ehtynyl-Trimehyl-Piperiodole complex deposited via spin coating. Current-voltage measurements showed the diodes followed the space charge limited current model. Analysis of this data determined how parameters like mobility, trap density, and threshold voltage varied with temperature, improving at higher temperatures. The study provided insight into charge transport within the organic semiconductor complex.
The document describes a simulation study comparing the RF and analog performance of different AlGaN/GaN MOSHEMT device structures. Single gate MOSHEMTs using SiO2, Al2O3, and HfO2 dielectrics were designed and simulated. Double gate and dielectric pocket double gate MOSHEMT structures were also simulated to improve performance. Simulation results showed the HfO2 dielectric pocket double gate MOSHEMT achieved the best performance with high drain current and transconductance, as well as high cutoff frequency over 1.95 THz, indicating suitability for analog and millimeter-wave applications.
The document summarizes research using spectroscopic ellipsometry to analyze Cu2ZnSnSe4 (CZTSe) thin films. Key findings include:
1) A refined model accounting for a ~220nm thick MoSe2 layer at the back contact improved the fit between measured and modeled ellipsometry data, allowing extraction of a more reliable CZTSe dielectric function.
2) Ellipsometry can detect the presence and thickness of secondary phase MoSe2 non-destructively.
3) Variations in dielectric functions between samples likely relate to composition variations and minor secondary phases.
This document summarizes a numerical simulation of a graded band gap GaAs/AlGaAs heterojunction solar cell performed with AMPS-1D modeling software. The simulation analyzed how a graded band gap region at the interface between the GaAs emitter and AlGaAs base layers affects solar cell performance. Results showed that a 0.14μm graded band gap region was needed to eliminate the conduction band spike and improve cell performance over an abrupt heterojunction. Photovoltaic parameters, including efficiency, of 31.1% were obtained for the cell with a graded interface, compared to 27.3% for an abrupt heterojunction cell.
The document discusses the design of an RF MEMS switch using COMSOL Multiphysics and Intellisuite simulation software. A cantilever beam switch structure is designed with dimensions and materials specified. Simulation results show the switch has a low actuation voltage of 4V, insertion loss of -8dB, and isolation of -40dB at 1.5GHz. To reduce the high resistance of a single switch, 10 switches are placed in parallel, lowering the effective resistance to 5.9 ohms. The switch performance is better at lower frequencies.
This document discusses the design and analysis of SRAM cells using tunneling field-effect transistors (TFETs) for ultralow-voltage operation. It analyzes the characteristics of TFET devices that impact SRAM performance, such as delayed saturation and broad crossover regions. Several published TFET SRAM cell designs are evaluated using technology computer-aided design simulations. The simulations show that the unidirectional conduction of TFETs degrades write stability. A novel 7-transistor driverless TFET SRAM cell is proposed to improve read, write, and hold stability through decoupled read paths and asymmetrical write-assist techniques.
TWO DIMENSIONAL MODELING OF NONUNIFORMLY DOPED MESFET UNDER ILLUMINATIONVLSICS Design
A two dimensional numerical model of an optically gated GaAs MESFET with non uniform channel doping has been developed. This is done to characterize the device as a photo detector. First photo induced voltage (Vop) at the Schottky gate is calculated for estimating the channel profile. Then Poisson’s equation for the device is solved numerically under dark and illumination condition. The paper aims at developing the MESFET 2-D model under illumination using Monte Carlo Finite Difference method. The results discuss about the optical potential developed in the device, variation of channel potential under different biasing and illumination and also about electric fields along X and Y directions. The Cgs under different illumination is also calculated. It has been observed from the results that the characteristics of the device are strongly influenced by the incident optical illumination.
Characterization of silicon tunnel field effect transistor based on charge pl...IJEECSIAES
The aim of the proposed paper is an analytical model and realization of the characteristics for tunnel field-effect transistor (TFET) based on charge plasma (CP). One of the most applications of the TFET device which operates based on CP technique is the biosensor. CP-TFET is to be used as an effective device to detect the uncharged molecules of the bio-sample solution. Charge plasma is one of some techniques that recently invited to induce charge carriers inside the devices. In this proposed paper we use a high work function in the source (ϕ=5.93 eV) to induce hole charges and we use a lower work function in drain (ϕ=3.90 eV) to induce electron charges. Many electrical characterizations in this paper are considered to study the performance of this device like a current drain (ID) versus voltage gate (Vgs), ION/IOFF ratio, threshold voltage (VT) transconductance (gm), and subthreshold swing (SS). The signification of this paper comes into view enhancement the performance of the device. Results show that high dielectric (K=12), oxide thickness (Tox=1 nm), channel length (Lch=42 nm), and higher work function for the gate (ϕ=4.5 eV) tend to best charge plasma silicon tunnel field-effect transistor characterization.
haracterization of silicon tunnel field effect transistor based on charge plasmanooriasukmaningtyas
The aim of the proposed paper is an analytical model and realization of the characteristics for tunnel field-effect transistor (TFET) based on charge plasma (CP). One of the most applications of the TFET device which operates based on CP technique is the biosensor. CP-TFET is to be used as an effective device to detect the uncharged molecules of the bio-sample solution. Charge plasma is one of some techniques that recently invited to induce charge carriers inside the devices. In this proposed paper we use a high work function in the source (ϕ=5.93 eV) to induce hole charges and we use a lower work function in drain (ϕ=3.90 eV) to induce electron charges. Many electrical characterizations in this paper are considered to study the performance of this device like a current drain (ID) versus voltage gate (Vgs), ION/IOFF ratio, threshold voltage (VT) transconductance (gm), and sub-threshold swing (SS). The signification of this paper comes into view enhancement the performance of the device. Results show that high dielectric (K=12), oxide thickness (Tox=1 nm), channel length (Lch=42 nm), and higher work function for the gate (ϕ=4.5 eV) tend to best charge plasma silicon tunnel field-effect transistor characterization.
Similar to Welcome to International Journal of Engineering Research and Development (IJERD) (20)
A Novel Method for Prevention of Bandwidth Distributed Denial of Service AttacksIJERD Editor
Distributed Denial of Service (DDoS) Attacks became a massive threat to the Internet. Traditional
Architecture of internet is vulnerable to the attacks like DDoS. Attacker primarily acquire his army of Zombies,
then that army will be instructed by the Attacker that when to start an attack and on whom the attack should be
done. In this paper, different techniques which are used to perform DDoS Attacks, Tools that were used to
perform Attacks and Countermeasures in order to detect the attackers and eliminate the Bandwidth Distributed
Denial of Service attacks (B-DDoS) are reviewed. DDoS Attacks were done by using various Flooding
techniques which are used in DDoS attack.
The main purpose of this paper is to design an architecture which can reduce the Bandwidth
Distributed Denial of service Attack and make the victim site or server available for the normal users by
eliminating the zombie machines. Our Primary focus of this paper is to dispute how normal machines are
turning into zombies (Bots), how attack is been initiated, DDoS attack procedure and how an organization can
save their server from being a DDoS victim. In order to present this we implemented a simulated environment
with Cisco switches, Routers, Firewall, some virtual machines and some Attack tools to display a real DDoS
attack. By using Time scheduling, Resource Limiting, System log, Access Control List and some Modular
policy Framework we stopped the attack and identified the Attacker (Bot) machines
Hearing loss is one of the most common human impairments. It is estimated that by year 2015 more
than 700 million people will suffer mild deafness. Most can be helped by hearing aid devices depending on the
severity of their hearing loss. This paper describes the implementation and characterization details of a dual
channel transmitter front end (TFE) for digital hearing aid (DHA) applications that use novel micro
electromechanical- systems (MEMS) audio transducers and ultra-low power-scalable analog-to-digital
converters (ADCs), which enable a very-low form factor, energy-efficient implementation for next-generation
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Influence of tensile behaviour of slab on the structural Behaviour of shear c...IJERD Editor
-A composite beam is composed of a steel beam and a slab connected by means of shear connectors
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stiffness and maximum shear force in composite beams subjected to hogging moment. The results show that the
shear studs located in the crack-concentration zones due to large hogging moments sustain significantly smaller
shear force and slip stiffness than the other zones. Moreover, the reduction of the slip stiffness in the shear
connection appears also to be closely related to the change in the tensile strain of rebar according to the increase
of the load. Further experimental and analytical studies shall be conducted considering variables such as the
reinforcement ratio and the arrangement of shear connectors to achieve efficient design of the shear connection
in composite beams subjected to hogging moment.
Gold prospecting using Remote Sensing ‘A case study of Sudan’IJERD Editor
Gold has been extracted from northeast Africa for more than 5000 years, and this may be the first
place where the metal was extracted. The Arabian-Nubian Shield (ANS) is an exposure of Precambrian
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includes the nations of Israel, Jordan. Egypt, Saudi Arabia, Sudan, Eritrea, Ethiopia, Yemen, and Somalia.
Arabian Nubian Shield Consists of juvenile continental crest that formed between 900 550 Ma, when intra
oceanic arc welded together along ophiolite decorated arc. Primary Au mineralization probably developed in
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originate as sea floor massive sulphide deposits.
The Red Sea Hills Region is a vast span of rugged, harsh and inhospitable sector of the Earth with
inimical moon-like terrain, nevertheless since ancient times it is famed to be an abode of gold and was a major
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rediscovered through time. Recent endeavours by the Geological Research Authority of Sudan led to the
discovery of a score of occurrences with gold and massive sulphide mineralizations. In the nineties of the
previous century the Geological Research Authority of Sudan (GRAS) in cooperation with BRGM utilized
satellite data of Landsat TM using spectral ratio technique to map possible mineralized zones in the Red Sea
Hills of Sudan. The outcome of the study mapped a gossan type gold mineralization. Band ratio technique was
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confirmed the existence of stock work of gold bearing quartz in the alteration zone. Another type of gold
mineralization that was discovered using remote sensing is the gold associated with metachert in the Atmur
Desert.
Reducing Corrosion Rate by Welding DesignIJERD Editor
This document summarizes a study on reducing corrosion rates in steel through welding design. The researchers tested different welding groove designs (X, V, 1/2X, 1/2V) and preheating temperatures (400°C, 500°C, 600°C) on ferritic malleable iron samples. Testing found that X and V groove designs with 500°C and 600°C preheating had corrosion rates of 0.5-0.69% weight loss after 14 days, compared to 0.57-0.76% for 400°C preheating. Higher preheating reduced residual stresses which decreased corrosion. Residual stresses were 1.7 MPa for optimal X groove and 600°C
Router 1X3 – RTL Design and VerificationIJERD Editor
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Active Power Exchange in Distributed Power-Flow Controller (DPFC) At Third Ha...IJERD Editor
This paper presents a component within the flexible ac-transmission system (FACTS) family, called
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transmission lines at the third-harmonic frequency. DPFC multiple small-size single-phase converters which
reduces the cost of equipment, no voltage isolation between phases, increases redundancy and there by
reliability increases. The principle and analysis of the DPFC are presented in this paper and the corresponding
simulation results that are carried out on a scaled prototype are also shown.
Mitigation of Voltage Sag/Swell with Fuzzy Control Reduced Rating DVRIJERD Editor
Power quality has been an issue that is becoming increasingly pivotal in industrial electricity
consumers point of view in recent times. Modern industries employ Sensitive power electronic equipments,
control devices and non-linear loads as part of automated processes to increase energy efficiency and
productivity. Voltage disturbances are the most common power quality problem due to this the use of a large
numbers of sophisticated and sensitive electronic equipment in industrial systems is increased. This paper
discusses the design and simulation of dynamic voltage restorer for improvement of power quality and
reduce the harmonics distortion of sensitive loads. Power quality problem is occurring at non-standard
voltage, current and frequency. Electronic devices are very sensitive loads. In power system voltage sag,
swell, flicker and harmonics are some of the problem to the sensitive load. The compensation capability
of a DVR depends primarily on the maximum voltage injection ability and the amount of stored
energy available within the restorer. This device is connected in series with the distribution feeder at
medium voltage. A fuzzy logic control is used to produce the gate pulses for control circuit of DVR and the
circuit is simulated by using MATLAB/SIMULINK software.
Study on the Fused Deposition Modelling In Additive ManufacturingIJERD Editor
Additive manufacturing process, also popularly known as 3-D printing, is a process where a product
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final shape of a product, 3-D printing develops the product from scratch thus obviating the necessity to cut away
materials. This prevents wastage of raw materials. Commonly used raw materials for the process are ABS
plastic, PLA and nylon. Recently the use of gold, bronze and wood has also been implemented. The complexity
factor of this process is 0% as in any object of any shape and size can be manufactured.
Spyware triggering system by particular string valueIJERD Editor
This computer programme can be used for good and bad purpose in hacking or in any general
purpose. We can say it is next step for hacking techniques such as keylogger and spyware. Once in this system if
user or hacker store particular string as a input after that software continually compare typing activity of user
with that stored string and if it is match then launch spyware programme.
A Blind Steganalysis on JPEG Gray Level Image Based on Statistical Features a...IJERD Editor
This paper presents a blind steganalysis technique to effectively attack the JPEG steganographic
schemes i.e. Jsteg, F5, Outguess and DWT Based. The proposed method exploits the correlations between
block-DCTcoefficients from intra-block and inter-block relation and the statistical moments of characteristic
functions of the test image is selected as features. The features are extracted from the BDCT JPEG 2-array.
Support Vector Machine with cross-validation is implemented for the classification.The proposed scheme gives
improved outcome in attacking.
Secure Image Transmission for Cloud Storage System Using Hybrid SchemeIJERD Editor
- Data over the cloud is transferred or transmitted between servers and users. Privacy of that
data is very important as it belongs to personal information. If data get hacked by the hacker, can be
used to defame a person’s social data. Sometimes delay are held during data transmission. i.e. Mobile
communication, bandwidth is low. Hence compression algorithms are proposed for fast and efficient
transmission, encryption is used for security purposes and blurring is used by providing additional
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transmission over cloud storage system.
Application of Buckley-Leverett Equation in Modeling the Radius of Invasion i...IJERD Editor
A thorough review of existing literature indicates that the Buckley-Leverett equation only analyzes
waterflood practices directly without any adjustments on real reservoir scenarios. By doing so, quite a number
of errors are introduced into these analyses. Also, for most waterflood scenarios, a radial investigation is more
appropriate than a simplified linear system. This study investigates the adoption of the Buckley-Leverett
equation to estimate the radius invasion of the displacing fluid during waterflooding. The model is also adopted
for a Microbial flood and a comparative analysis is conducted for both waterflooding and microbial flooding.
Results shown from the analysis doesn’t only records a success in determining the radial distance of the leading
edge of water during the flooding process, but also gives a clearer understanding of the applicability of
microbes to enhance oil production through in-situ production of bio-products like bio surfactans, biogenic
gases, bio acids etc.
Gesture Gaming on the World Wide Web Using an Ordinary Web CameraIJERD Editor
- Gesture gaming is a method by which users having a laptop/pc/x-box play games using natural or
bodily gestures. This paper presents a way of playing free flash games on the internet using an ordinary webcam
with the help of open source technologies. Emphasis in human activity recognition is given on the pose
estimation and the consistency in the pose of the player. These are estimated with the help of an ordinary web
camera having different resolutions from VGA to 20mps. Our work involved giving a 10 second documentary to
the user on how to play a particular game using gestures and what are the various kinds of gestures that can be
performed in front of the system. The initial inputs of the RGB values for the gesture component is obtained by
instructing the user to place his component in a red box in about 10 seconds after the short documentary before
the game is finished. Later the system opens the concerned game on the internet on popular flash game sites like
miniclip, games arcade, GameStop etc and loads the game clicking at various places and brings the state to a
place where the user is to perform only gestures to start playing the game. At any point of time the user can call
off the game by hitting the esc key and the program will release all of the controls and return to the desktop. It
was noted that the results obtained using an ordinary webcam matched that of the Kinect and the users could
relive the gaming experience of the free flash games on the net. Therefore effective in game advertising could
also be achieved thus resulting in a disruptive growth to the advertising firms.
Hardware Analysis of Resonant Frequency Converter Using Isolated Circuits And...IJERD Editor
-LLC resonant frequency converter is basically a combo of series as well as parallel resonant ckt. For
LCC resonant converter it is associated with a disadvantage that, though it has two resonant frequencies, the
lower resonant frequency is in ZCS region[5]. For this application, we are not able to design the converter
working at this resonant frequency. LLC resonant converter existed for a very long time but because of
unknown characteristic of this converter it was used as a series resonant converter with basically a passive
(resistive) load. . Here, it was designed to operate in switching frequency higher than resonant frequency of the
series resonant tank of Lr and Cr converter acts very similar to Series Resonant Converter. The benefit of LLC
resonant converter is narrow switching frequency range with light load[6] . Basically, the control ckt plays a
very imp. role and hence 555 Timer used here provides a perfect square wave as the control ckt provides no
slew rate which makes the square wave really strong and impenetrable. The dead band circuit provides the
exclusive dead band in micro seconds so as to avoid the simultaneous firing of two pairs of IGBT’s where one
pair switches off and the other on for a slightest period of time. Hence, the isolator ckt here is associated with
each and every ckt used because it acts as a driver and an isolation to each of the IGBT is provided with one
exclusive transformer supply[3]. The IGBT’s are fired using the appropriate signal using the previous boards
and hence at last a high frequency rectifier ckt with a filtering capacitor is used to get an exact dc
waveform .The basic goal of this particular analysis is to observe the wave forms and characteristics of
converters with differently positioned passive elements in the form of tank circuits.
Simulated Analysis of Resonant Frequency Converter Using Different Tank Circu...IJERD Editor
LLC resonant frequency converter is basically a combo of series as well as parallel resonant ckt. For
LCC resonant converter it is associated with a disadvantage that, though it has two resonant frequencies, the
lower resonant frequency is in ZCS region [5]. For this application, we are not able to design the converter
working at this resonant frequency. LLC resonant converter existed for a very long time but because of
unknown characteristic of this converter it was used as a series resonant converter with basically a passive
(resistive) load. . Here, it was designed to operate in switching frequency higher than resonant frequency of the
series resonant tank of Lr and Cr converter acts very similar to Series Resonant Converter. The benefit of LLC
resonant converter is narrow switching frequency range with light load[6] . Basically, the control ckt plays a
very imp. role and hence 555 Timer used here provides a perfect square wave as the control ckt provides no
slew rate which makes the square wave really strong and impenetrable. The dead band circuit provides the
exclusive dead band in micro seconds so as to avoid the simultaneous firing of two pairs of IGBT’s where one
pair switches off and the other on for a slightest period of time. Hence, the isolator ckt here is associated with
each and every ckt used because it acts as a driver and an isolation to each of the IGBT is provided with one
exclusive transformer supply[3]. The IGBT’s are fired using the appropriate signal using the previous boards
and hence at last a high frequency rectifier ckt with a filtering capacitor is used to get an exact dc
waveform .The basic goal of this particular analysis is to observe the wave forms and characteristics of
converters with differently positioned passive elements in the form of tank circuits. The supported simulation
is done through PSIM 6.0 software tool
Amateurs Radio operator, also known as HAM communicates with other HAMs through Radio
waves. Wireless communication in which Moon is used as natural satellite is called Moon-bounce or EME
(Earth -Moon-Earth) technique. Long distance communication (DXing) using Very High Frequency (VHF)
operated amateur HAM radio was difficult. Even with the modest setup having good transceiver, power
amplifier and high gain antenna with high directivity, VHF DXing is possible. Generally 2X11 YAGI antenna
along with rotor to set horizontal and vertical angle is used. Moon tracking software gives exact location,
visibility of Moon at both the stations and other vital data to acquire real time position of moon.
“MS-Extractor: An Innovative Approach to Extract Microsatellites on „Y‟ Chrom...IJERD Editor
Simple Sequence Repeats (SSR), also known as Microsatellites, have been extensively used as
molecular markers due to their abundance and high degree of polymorphism. The nucleotide sequences of
polymorphic forms of the same gene should be 99.9% identical. So, Microsatellites extraction from the Gene is
crucial. However, Microsatellites repeat count is compared, if they differ largely, he has some disorder. The Y
chromosome likely contains 50 to 60 genes that provide instructions for making proteins. Because only males
have the Y chromosome, the genes on this chromosome tend to be involved in male sex determination and
development. Several Microsatellite Extractors exist and they fail to extract microsatellites on large data sets of
giga bytes and tera bytes in size. The proposed tool “MS-Extractor: An Innovative Approach to extract
Microsatellites on „Y‟ Chromosome” can extract both Perfect as well as Imperfect Microsatellites from large
data sets of human genome „Y‟. The proposed system uses string matching with sliding window approach to
locate Microsatellites and extracts them.
Importance of Measurements in Smart GridIJERD Editor
- The need to get reliable supply, independence from fossil fuels, and capability to provide clean
energy at a fixed and lower cost, the existing power grid structure is transforming into Smart Grid. The
development of a smart energy distribution grid is a current goal of many nations. A Smart Grid should have
new capabilities such as self-healing, high reliability, energy management, and real-time pricing. This new era
of smart future grid will lead to major changes in existing technologies at generation, transmission and
distribution levels. The incorporation of renewable energy resources and distribution generators in the existing
grid will increase the complexity, optimization problems and instability of the system. This will lead to a
paradigm shift in the instrumentation and control requirements for Smart Grids for high quality, stable and
reliable electricity supply of power. The monitoring of the grid system state and stability relies on the
availability of reliable measurement of data. In this paper the measurement areas that highlight new
measurement challenges, development of the Smart Meters and the critical parameters of electric energy to be
monitored for improving the reliability of power systems has been discussed.
Study of Macro level Properties of SCC using GGBS and Lime stone powderIJERD Editor
The document summarizes a study on the use of ground granulated blast furnace slag (GGBS) and limestone powder to replace cement in self-compacting concrete (SCC). Tests were conducted on SCC mixes with 0-50% replacement of cement with GGBS and 0-20% replacement with limestone powder. The results showed that replacing 30% of cement with GGBS and 15% with limestone powder produced SCC with the highest compressive strength of 46MPa, meeting fresh property requirements. The study concluded that this ternary blend of cement, GGBS and limestone powder can improve SCC properties while reducing costs.
Study of Macro level Properties of SCC using GGBS and Lime stone powder
Welcome to International Journal of Engineering Research and Development (IJERD)
1. International Journal of Engineering Research and Development
e-ISSN: 2278-067X, p-ISSN : 2278-800X, www.ijerd.com
Volume 5, Issue 3 (December 2012), PP. 68-86
Matlab Based Static I-V Characteristics of Optically
Controlled GaAs MESFET’S
Sanjay.C.Patil1, B.K.Mishra2
1
(Research Scholar at NMIMS (MUMBAI), Parshvanath College of Engineering,
THANE (W), MUMBAI, 400601 INDIA
3
Thakur College of Engineering and Technology, Kandivali (E) MUMBAI, 400101 INDIA
Abstract: - Optoelectronic is one of the thrust areas for the recent research activity. One of the key
components of the optoelectronic family is photo detector to be widely used in broadband
communication, optical computing, optical transformer, optical control etc. Result’s that theoretical
predicted for device and using MATLAB are quite similar A new analytical model for the static I-V
characteristics of GaAs MESFET’s under optically controlled conditions in both linear and saturation
region is presented in this paper. The novelty of the model lies in characterizing both photovoltaic
(external, internal) and photoconductive effects. Deep level traps in the semi insulating GaAs substrate
are also included in this model. Finally, effect of backgate voltage on I-V characteristics is explained
analytically for the first time in literature. Small signal parameters of GaAs MESFET are derived under
both dark and illuminated conditions.
Keywords: - Optically controlled GaAs MESFET, photo voltage, deep level traps, backgating, and
channel length modulation.
I. INTRODUCTION
Optically controlled GaAs MESFET (OPFET) is the considered key device used for the design of
photo-detector [1-3]. It is experimentally established fact that optical radiation incident on the transparent or
semitransparent gate of the device is used to control the microwave characteristics of the OPFET [4-5]. It has
also been investigated that many of the microwave characteristics of GaAs MESFET like resonant frequency,
transit time etc., can be controlled by controlling the internal gate-source and gate-drain capacitances of the
device [6-7]. Here it is worth mention that the level of incident illumination can change the charge distribution
under the gate that determines the internal capacitances of the GaAs MESFET. Therefore the internal
capacitances of GaAs MESFET can also be controlled by the incident illumination.
Optical control of microwave devices and circuits has been a fertile area of research for the past two
decades [1]. In particular, optically controlled GaAs MESFET’s (OPFET’s) have drawn considerable attention
as potential active devices in photo detector as well as in OEIC’s [2-9]. Optical control has many advantages
for complex microwave systems such as size reduction, signal isolation, large bandwidth and immunity to
electromagnetic interference. With such numerous advantages many potential application like optically
controlled amplifiers, oscillators, Light Amplifying Optical Switch (LAOS) and phase shifters, to name a few,
become feasible [3-5, 7-9]. The possibility of making use of optical sensitivity of MESFET to form an
additional signal input port justifies an increased interest in physical mechanism which occurs when MESFET is
illuminated. When photonic MMIC is designed in such a way as to involve the optical phenomenon mentioned
above, the circuit designer is immediately aware of the necessity of a good model with all major effects
considered. Several researchers experimentally showed that gain, drain current and S-parameters of GaAs
MESFET can be controlled by varying incident light on the device in the same manner as varying the gate bias
voltage [4, 7-9].
Modeling of I-V characteristics of optically controlled GaAs MESFET has been carried out over the
years by several researchers. Salles [7] reported an over simplified analytical model for the I-V characteristics of
GaAs MESFET under optically controlled conditions and estimated changes in MESFET small signal
parameters due to illumination. Simons [10] derived analytical expressions for I-V characteristics of different
types of FET configurations under optical illumination on the devices. He also computed variations in FET
small signal parameters such as transconductance, channel conductance with illumination. Singh et al. [11]
reported an analytical model for the drain-source current of optically controlled GaAs MESFET. Chakrabarti et
al. [12] presented an analytical model for the photo-dependent I-V characteristics of GaAs MESFET and
explained their results by means of both the excess photo-generated carriers in the depletion region and the
photo voltage developed across the Schottky junction. Since, excess holes in the depletion region due to the
68
2. MATLAB Based Static I-V Characteristics Of Optically Controlled Gaas MESFET’s
illumination develop photo voltage across the Schottky junction, inclusion of both these effects (photo-
generated excess carriers and photo-induced gate voltage) simultaneously seems to be ambiguous. Further, they
also ignored the effect of excess photo-generated carriers in the neutral region. Moreover, the resultant model
was very complex as compared to Singh et al. [11]. Kawasaki et al. [4] demonstrated an illuminated FET model
by including an illumination intensity parameter in the modified Statz model with a large number of unknown
fitting parameters to be extracted either from extensive experimental or from simulation results. Some two-
dimensional numerical models of optically controlled GaAs MESFET’s are also reported in the literature [13] In
this paper we present an analytical modeling of static I-V characteristics of optically controlled GaAs
MESFET’s in both linear and saturation regions of operation. A comprehensive analytical characterization of
photo induced voltages (both internal and external) and photoconductive current in the channel is presented.
Deep level traps in the semi insulating substrate as well as in the active layer are considered through which the
important effect, backgating is analytically modeled for the first time in the literature under illuminated
conditions. In linear region gradual channel approximation is used and in saturation region channel length
modulation is considered as a source of finite output conductance. Later, small signal parameters of GaAs
MESFET under optically controlled conditions are derived from the static I-V characteristics.
II. THEORETICAL MODEL
The schematic structure of a non-self-aligned GaAs MESFET is shown in Fig 1. Gate area of the
device is illuminated with monochromatic light of energy greater than or equal to the band gap energy of GaAs.
The metal gate used for the Schottky contact is assumed to be transparent/ semitransparent to the incident light
[5, 11-12]. The substrate of the device is assumed to be an undoped high-pure LEC semi-insulating GaAs
material. The active channel region of the device is an n-GaAs layer which can be obtained by ion implanting Si
into the SI substrate.
Fig.1. schematic of Gaas MESFET
In Fig. 1, the depletion region at y=0,is a conventional depletion region of Schottky gate and the other
depletion region is formed at the channel-substrate interface (at y=a) due to the deep level traps in the SI
substrate [15, 18]. We call the above two depletion regions as front and back depletion regions respectively. The
widths of these depletion regions are strongly dependent on the substrate properties as well as on the backgate
voltage which in turn effects current flowing through the channel. Thus, substrate induced effects are crucial in
determining I-V characteristics of the device.
1. Modeling of the Deep Level Traps and Backgating Effects
One method for rendering undoped GaAs wafers semi-insulating is through the careful control of melt
stoichiometry during LEC growth. It has been shown that a slight excess of As in the melt favors the formation
of EL2 deep donors that compensates residual shallow acceptors (C from B O encapsulant) and shallow donors
2 3
(S or Si) [15]. The probability of an EL2 level to be occupied by an electron in the SI-substrate under thermal
equilibrium condition is given by the Fermi function [18].
(E E )
1 T fs 1
f ( EL 2 ) {1 g exp[ ]} (1)
eql
kT
Where E energy of the EL2 level E is the Fermi energy level in the substrate bulk, g 2 is the
T fs
degeneracy factor of EL2.
69
3. MATLAB Based Static I-V Characteristics Of Optically Controlled Gaas MESFET’s
The position of Fermi level in the substrate bulk can be obtained from charge neutrality condition in the substrat
N N N p n 0 ( 2)
EL 2 ,S SD SA sub sub
where
(E E
fs T 1
N N (1 f ( EL 2 ) N {1 2 exp[ ]}
EL 2 ,S EL 2 eql EL 2
kT
is the density of ionized EL2 traps, n ,p N N and N N are the free electron, hole,
sub sub SD SA
SD SA
ionized shallow donor and ionized shallow acceptor concentrations in the bulk substrate under equilibrium
condition respectively. Since n and p are negligibly small as compared to other ionized impurities of
sub sub
equation (2), we may write
N N N
EL 2 SD SA
Ec E ( E c E ) kT ln( ) ( 3)
fs T
2( N N )
SA SD
Under steady-state non-equilibrium condition, the Fermi statistics described by Eqn (1) becomes invalid. In this
case, the Fermi function can be given by
e p nC n
f ( EL ) ( 4)
noneql 2
e ne pC
p n p
Where C p v andC n v
p pth n nth
Are the electron and hole capture coefficients σ and σ are the capture cross section of holes and electrons ;n
p n
and p are the electron and hole concentration under non-equilibrium conditions ; v and v are the
pth nth
thermal velocities of holes and electrons; e and e n are the emission rates of holes and electrons from EL2
p
levels respectively
The formation of the back depletion region at the channel-substrate interface is due to the fact that
some of the free electrons in the channel gain sufficient energy and enter into the substrate. These electrons are
captured by the EL2 traps and a negative space charge region is created at the substrate side [15]. As a result, a
depletion region is created at the backside of the channel. The negative charge density accumulated in the
substrate can be determined as follows:
Since and n & p are negligible in the semi-insulating substrate, the concentration of neutral EL2 states
in the substrate side near the channel-substrate (CS) interface under steady-state non-equilibrium condition is
given by
70
4. MATLAB Based Static I-V Characteristics Of Optically Controlled Gaas MESFET’s
0
N ( non eql ) N f ( EL 2 ) n p 0
EL 2 EL 2 non _ eql
ep
N
EL 2
[ ] (5)
en e p
The concentration of negative charge in the substrate side of the CS junction is,is the density of
occupied EL2 traps in the bulk substrate under thermal equilibrium condition.
Neglecting the free carrier concentrations in the depletion regions (i.e.0==pn), the concentration of ionized EL2
states in these depletion regions may be given by
0 0
N N ( non epl ) N ( egl )
EL 2 EL 2
sub
e 1 (E E
p T fs 1
{ N EL 2 [ ]} { N EL 2 {1 exp[ ]} } ( 6 )
e p en 2 kT
Where
0
N ( eql ) N f ( EL 2 )
EL 2 EL 2 eql
1 (E E )
T fs 1
N
EL 2
{1 exp[ ]}
2 kT
Is the density of occupied EL2 traps in the bulk substrate under thermal equilibrium condition.
Neglecting the free carrier concentrations in the depletion regions (i.e. n = p = 0), the concentration of ionized
EL2 states in these depletion regions may be given by
ep
D
N
EL 2
N
EL 2
(1 f
non _ eql
( EL 2 )
n p 0
) N
EL 2
[ ] - (7)
e e
n p
Assuming that N N and N are fully ionized in the active layer .The total positive charge concentration
d , SD SA
in depletion layer becomes
D
N N N N N (8)
dep d SD EL 2 SA
A number of experimental and theoretical investigation reported in literature [16,19] suggest that There exists a
backgating threshold voltage V , such that if the backgate voltage V is below certain threshold voltage
thbg b
V , substrate maintains high resistance with the backgate voltage drops primarily across the bulk substrate
thbg
and has little effect on the channel thickness. But, when V exceeds V (i.e V > V .), impact ionization
b thbg bg thbg
of deep traps occurs and the semi insulating substrate transits from a state of high resistivity to low resistivity
with the difference V V drops across the CS interface thus widening the back depletion region and
bg thbg
71
5. MATLAB Based Static I-V Characteristics Of Optically Controlled Gaas MESFET’s
narrowing the channel. To include the effect of V , voltage across the CS junction for V 0 is expressed in
bg ds
the following form
V
ch s
{Vbics ; V V
bg thbg
{V (V V ); V V (9 )
bics bg thbg bg thbg
Where V is the built-in potential across the channel-substrate junction. Note that the absolute value of the
bics
substrate bias V is assumed in Eqn (9). Here we have considered V as a parameter without going through
bg thbg
details of modeling, details of exact modeling V can be found elsewhere [19].
thbg
We can model the additional voltage f (V ) (say) added to the gate as
bg
f (V ) { 0 ; V V
bg bg thbg
2
{α ( V V ) α ( V V ) ;V V (10 )
bg thbg bg thbg bg thbg
1 2
the height of front depletion region at a distance x below the gate including V is
bg
f 2
s
h ( x) (V V f (V ) V ( x ) (11)
bg bi gs bg
qN
dep
Where s is permittivity of GaAs, V is built-in potential across Schottky junction and V ( x ) is the channel
bi
potential at any distance x measured with respect to the source.
Similarly, the height of back depletion region measured from channel-substrate interface(y=a) including
backgating can be obtained by solving one dimensional Poisson’s equation with appropriate boundary
conditions [19]
N
b 2 s
sub
h
bg
( x)
{ }(Vchs V ( x )) (12)
qN N
N
dep
dep sub
Now ,the pinch-off voltage of the device may be written as
72
6. MATLAB Based Static I-V Characteristics Of Optically Controlled Gaas MESFET’s
qN
dep b 2
V po (a h ( L) V )
bg ds0
2 s
qN 2 V N
dep s ch s
[a { sub
}]2 (13)
2 qN N N
s dep dep sub
Threshold voltage of the MESFET V including backgating is
th
qN 2 V N
dep s ch s
V (V f (V )) { [a { sub
}]2 } (14)
th bi bg 2 qN N N
s dep dep sub
It is noted that for N N N 0 and V 0 the thresh hold voltage equals to
SD SA
EL 2 bg
qN a 2
d
V which is the same as that of the conventional MESFET’s
bg 2
s
2. Modeling of Photovoltaic Effects
Let be the incident photon flux density (i.e. number of photons per unit area per second) at y=0.
0
Now can be expressed in terms of input optical power as [12]
0
(1 R )(1 R ) P
m s in
(15 )
0
hZL
where P is the incident optical power, h is the Planck’s constant, is the frequency of incident light, Z is the
in
width of the gate-metal R m and R s are the reflection coefficients for normal incidence at metal surface and
metal-semiconductor interface, respectively.
Since optical transmission through gate depends on thickness of gate metallization, the metal used for
Schottky contact (such as gold) should be made sufficiently thin (~100 Å) to achieve higher transmittance up to
90-95% [5] at the cost of lower unity-gain frequency and higher noise figure. More recently some alternate
materials are suggested such as Indium Tin Oxide (ITO) and Al or Ga doped ZnO [22-23]. These thin films are
highly degenerate n-type semiconductors with low resistivity. Being wide band gap materials, these are
transparent to visible light with transmittance up to 90%in the operating wavelength range500nm-900nm and
form good Schottky contact with GaAs [22]. However, we have considered a semi-transparent/transparent gate
with transmittance as a parameter (which can be determined by R m and R s as defined in Eqn 15) for different
metals used for the Schottky contact. When GaAs MESFET is illuminated with optical radiation on the gate
73
7. MATLAB Based Static I-V Characteristics Of Optically Controlled Gaas MESFET’s
area, absorption of photons takes place in the active channel region as well as in the substrate region of the
device. The absorption of light results in the generation of electron-hole pairs in both depletion regions and in
the neutral channel. Holes generated in gate-depletion and back-depletion regions are drifted out toward the
metal and semi-insulating sides respectively due to the strong electric fields present in depletion regions. Photo-
generated excess holes in the neutral channel region are diffused into the front and back depletion regions and
are also finally swept out. Further, the photo-generated electrons in the substrate near the channel-substrate
junction are also drifted into the active layer of the device. Thus, incident illumination results in two
photocurrents: one flows from the active layer to the gate-metal and the other flows from active layer to the
semi-insulating substrate. This results in developing photo-voltages across the Schottky junction (i.e. external
photo voltage) [7] and the channel-substrate junction (i.e. internal photo voltage) [12]. However, due to the
relatively complex structure of the depletion regions of the MESFET, we have assumed that the above induced
photo-voltages are independent of the external biasing voltages, which is conformed by several experimental
results [8, 13, 24].
i) Derivation of external photovoltage
f ch
Let P ( y ) and P ( y ) be the photo-generated hole densities in the front depletion and neutral regions of the
channel respectively. Assuming that the excess holes generated in the depletion region are swept out with
f ch
saturation velocity towards the metal, P ( y ) and P ( y ) may be obtained by solving the following steady
state continuity equations [21]:
f f f
p ( y) p ( y) 2 p ( y)
G V (D ) 0 (16)
opt p y p y 2
p
( p ch p )
2 p ch ( y )
D G
no
0 (17 )
p y 2 opt
p
y
Where is the G e photo-generation rate of excess carriers, p is the hole concentration in the
opt 0 no
active layer under dark condition. ( 1 / V N [18], V and D are the recombination lifetime,
p p pth EL 2 p p
saturation velocity and diffusion coefficient of holes respectively. Note that the last term in the left hand side of
Eqn (16) has been intentionally introduced to represent the diffusion of excess holes from bulk towards
semiconductor-metal interface to include the surface recombination effect at that interface.
We may solve Eqn (16) using the following boundary conditions [21]:
f
f f p f
p (y h ) 0, D
( y)
S p ( 0 ) (18)
o p y y 0 pm
74
8. MATLAB Based Static I-V Characteristics Of Optically Controlled Gaas MESFET’s
Where S ( V N ) is the surface recombination velocity of holes at y=0 with surface state density
pm p pth st
2
12 2 f s
as N ( 1 X 10 cm ) [18] and h V is the height of schottky depletion region
st o qN bi
dep
With no external bias.
First boundary condition of Eqn (18) states that excess hole concentration at depletion edge is very
small due to the strong fields in the depletion region [21] where as second boundary condition represents the
diffusion of excess holes towards the surface and eventual recombination at y=0
Now the photocurrent due to the excess holes generated in the front depletion region is
f
f f p f f
J ( y) qV p ( y) qD
( y)
qV p ( 0 ) qS p ( 0 ) (19 )
dep y 0 p y 0 p y y 0 p pm
The diffusion current component of excess holes in neutral region can be obtained by solving Eqn (17)
with the following boundary conditions [21]
(p
ch
p ) 0
no f
y h
o
(p
ch
p ) 0 ( 20 )
no y a hb
o
2 N
b s sub
Where h ( V )
is back depletion width from y=0 into the channel due to the
o qN N N
bics
dep dep sub
channel- substrate junction under no bias conditions. From Eqn (17), excess hole density in the neutral channel
due to illumination is given by
f
b y h
f ( a hb y ( a hb )
) e y ] ( 21)
ch 0 p e 0 o e o 0
p ( y) p [ sinh ( ) sinh (
no 2 L2 p 1 L L
p p
f
h ( a hb )
o o
Where sinh [ ] and L D is the diffusion length of holes
L p p p
p
75
9. MATLAB Based Static I-V Characteristics Of Optically Controlled Gaas MESFET’s
The resulting photocurrent density flowing from the active layer to the metal due to the diffusion of
excess holes generated in the neutral region at depletion edge is
ch ( y )
J
ch
(h
f
) qD ( p ) ( 22 )
diff o p y f
y h
o
Total photo current density flowing from semiconductor to metal at the gate junction is
J J f (0) J ch (h
f
) ( 23)
total depf diff o
The photo induced voltage developed across the Schottky junction is [5, 7, 12]
J
nkT total
V (
ln 1 ) ( 24 )
op q J
s
Where’n’ is ideality factor, k is Boltzmann’s constant, T is the operating temperature, q is electron charge and
J is reverse saturation current density of the Schottky junction
s
ii) Derivation of internal photo voltage
Since the substrate-depletion region is much larger than that of the back depletion region [15] and the
absorption coefficient of GaAs at wave length is 0.83m it may be assumed that for the substrate heigh
D 10 m 1 / , most of the absorption take place within the front, back and substrate-depletion regions.
Hence optical absorption in the neutral region of the substrate may be neglected. The photo-voltage developed
across the channel-substrate junction may be determined as below:
Photo-generated holes in the neutral channel are diffused into the back depletion region as well, diffusion
current density at the edge of the back depletion region may be obtained in a similar manner as considered
previously and may be written from Eqn (22)
p ch ( y )
J
ch b
( a h ) qD ( 25 )
diff o p y b
y a h
o
b b
Let p ( y ) be the excess photo generated hole density in the back depletion region. p ( y ) may be obtained
by solving
p b pb
V G 0 ( 26 )
p y opt
p
b
Using boundary condition p [21]. The solution of Eqn (26) is
y a hb 0
o
76
10. MATLAB Based Static I-V Characteristics Of Optically Controlled Gaas MESFET’s
b 0 p y
p ( y) {exp[ ( a h b )( 1
] exp[ y ] ( 27 )
) }
V 1 V o V
p p p p p p
The hole drift current density at channel-substrate boundary (y =a )is thus obtained as
b b
J ( y a ) qV p ( y a ) ( 28)
dr p
Now, the photo generated electrons in the substrate depletion region are also drifted towards the back
depletion region resulting in a photocurrent component flowing from the channel to substrate side. The photo-
ss
generated electron density n ( y ) in the substrate-depletion region of channel-substrate junction may be
obtained by solving [21]
n ss n ss
V G 0 ( 29 )
n y opt
n
Where V and ( 1 / V N ) are saturation velocity and recombination lifetime of electron in the
n n n nth EL 2
ss
substrate depletion region respectively .Using the boundary conditions n [21]
y a h ss 0
o
We may obtain
ss y
n ( y)
0 n
{exp[ ( a h ss )( 1
) ] exp[y ]} ( 30 )
V 1 o V V
n n n n n n
N 2 N
ss d s sub
Where h ( ) {
}(V ) is the assumed
o N N qN
bics N
sub dep dep sub
Height of the substrate-depletion region from y=a under no bias condition. The electron drift current
density at CS interface flowing from substrate into channel is
ss ss
J ( y a ) qV n ( y a ) ( 31)
dr n
Hence, the total photo current density flowing from the active layer to the substrate is
ch cs ch b b ss
J J ( a h ) J ( a ) J ( a ) ( 32 )
total diff 0 dr dr
The photo voltage developed across this junction can be written as [12, 24],
77
11. MATLAB Based Static I-V Characteristics Of Optically Controlled Gaas MESFET’s
J ch cs
nkT total
V ln(1 ) ( 33)
opt q J ch cs
s
Where is the reverse saturation current density at channel-substrate junction
iii) Photo conductive current
Along with photovoltaic effects photoconductive effects in active channel also manifests when the
device is illuminated. Overall photo response of the device to optical illumination will be the superposition of
both components considering one at a time. In the previous subsections we modeled photovoltaic effects without
considering photoconductive effects. In this subsection we tried to quantify photoconductive effects.
Photo generated holes and electrons in the channel due to incident illumination contribute to the
photoconductive current in the active region. Associated photoconductive current density can be expressed in
terms of these carrier concentrations as
ch ch
J q(n V p V ) ( 34 )
pc n p
n ch p ch
( 35)
n p
f b
Interating ZJ from y h to y a h
pc bg bg
b
y a hb y a hb y a h
bg bg bg
n n ch
I ZJ dy Z P ch q ( V V ) dy Zq ( V V ) P dy ( 36 )
pc pc n p n p
f f f
y h y h p y h p
bg bg bg
in GaAs MESFET’s the channel height is in sub-micron regime, diffusion length is several microns (typically 2-
6
10μm) and the absorption coefficient is in the range 1 4 X 10 / m for wavelengths 0.65-0.85-microns hence
f b
a h h
bg bg
it is wise enough to assume . 1
Lp
Final simplified expression for photoconductive current after several approximations is
f
2 h
0 p f b 2 bg
I 0.5 Zq [ n V V ][ a h h ] e ( 37 )
pc 2 L2 1 n p bg bg
p
78
12. MATLAB Based Static I-V Characteristics Of Optically Controlled Gaas MESFET’s
it can be seen that photoconductive current is a strong function of gate-source voltage and device parameters. As
f b
V increases negatively effective channel opening a h h decreases and photoconductive current
gs bg bg
also decreases. Due to square dependence of I on effective channel opening magnitude of I is generally
pc pc
in sub- microampere range
3. I-V Characteristics of GaAs MESFET under Illumination
De Salles [7] has shown experimentally that if a high resistance (≥k50 Ω) is connected at the gate
biasing circuit, photo-voltage developed across Schottky junction is superimposed on gate voltage. The effective
gate-source bias under illumination becomes
V V V ( 38)
opgs gs op
Similarly, the photo-voltage developed across the channel-substrate junction will change the built-in
potential across the junction [24]. It was also confirmed by 2-D numerical simulations [13]. The effective built-
in potential under illuminated condition will be
V V V ( 39 )
opbi bics opcs
Drain-source current of GaAs MESFET under illuminated condition will be the superposition of both
photovoltaic and photoconductive effects
I I I ( 40 )
ds pv pc
Where I is final drain-source current, I is drain-source current including photovoltaic effect only
ds pv
and I is the photoconductive current in the channel region of MESFET.
pc
The height of Schottky and back depletion regions from y=0and y=a in linear region under illuminated
condition can be obtained by substituting Eqn. (38-39) in Eqn. (11-12).
Later, an analytical model I-V model has been developed by including deep level traps and backgating under
optically controlled conditions. Using the assumption of a uniform doping profile and a gradual channel
approximation with the depletion region forming at channel-substrate junction, drain-source current in linear
region can be expressed as [21]:
f b
I qZ ( N N ) ( a h ( x) h ( x )) ( 41)
pv d sub x bg bg
dV
Where is electric field along the x-direction in the channel and last term represents the effective
x dx
channel opening restricted by both depletion regions.
If the source and drain parasitic resistances are neglected, integrating Eqn (41) from x=0 to x=L yields the
analytical expression for the I-V characteristics in linear region.
79
13. MATLAB Based Static I-V Characteristics Of Optically Controlled Gaas MESFET’s
Z q ( N N )
V
ds f b
n d sub
I ( a h ( x) h ( x )) dv I
ds L bg bg pc
0
3 3
V V V f (V ) V V V f (V )
ds opgs bg bi bi opgs bg
A 3( [ ds
) 2( )2 ( 2
) ] ( 42)
V V V
po po po
Z q 2 ( N N )( N ) a 3
n d sub dep
Where A is a constant
6 . L
Equation (42) is strictly valid up to the onset of saturation when electric field in the channel reaches saturation
1 1 1
electric field E at V V [( V ) ( )] therefore I at the onset of velocity
s ds sat V th E L ds sat
opgs s
saturation is I I (V V ).
ds sat ds ds sat
In deriving Eqn. (41), we implicitly assumed that the channel length is constant. When MESFET is biased in
saturation region depletion regions at drain end of gate extends laterally into the channel reducing the effective
channel length. In a physical model, channel length modulation is the phenomenon producing finite output
conductance in saturation region. The effective channel length of MESFET in saturation region is
L L L ( 43)
eff s
(V V
s ds sat ) 1
Here L 2.06 K [ ] is the length of velocity Saturation region below gate [25], K is
s d a n N 2 d
cr d
a domain parameter [25] and n is the characteristic doping density of GaAs.
cr
Analytical expression for I-V characteristics in saturation region is, I I (L L )
ds ds sat eff
3 3
V V V f (V ) V V V f (V )
sat opgs bg bi bi opgs bg
I A {3[ sat
] 2[( )2 ( 2
) ]
ds eff V V V
po po po
3 3
N V V V V V
sat ch s opcs ch s opcs
2[
sub
][( )2 ( ) 2 ]} I ( 44 )
N N V V pc
dep sub po po
80
14. MATLAB Based Static I-V Characteristics Of Optically Controlled Gaas MESFET’s
Where A A
eff L L
eff
The first two terms in (44) are similar to the conventional analytical I-V model with gradual channel
approximation and abrupt depletion layer [21]. Reduction in the drain current due to back depletion region
which in turn due to the presence of deep level traps in the substrate is evident from the last term of (43).
Backgating further reduces drain current by increasing the width of both depletion regions. Finally intrinsic
small signal parameters like transconductance and output conductance of GaAs MESFET can be derived from
the modeled I-V characteristics.
Tran conductance and drain-source resistance under illuminated conditions are
I V
ds ds
g and R (45)
m V V ds I V
gs ds const ds gs const
III. RESULTS AND DISCUSSION
Photo-induced voltage across Schottky junction is presented in Fig 2(a) (dashed line) as a function of
incident optical power with the device parameters in [7, 9]. The gate metal is assumed to be a semi transparent
22 3
one with R and R as 0.65 and 0.2 respectively. The values of N 1 X 10 m
EL2,
m s
21 3 20 3 18 2 18 2
N 1.1 X 10 m , N 1 X 10 m , 1 X 10 m and 3 X 10 m
SA EL2,
n p
.[18]
It is observed that in fig 2(a) the external photo voltage increased with increased in incident optical
power of 0.3mW is approximately 0.345V,which is closed to experimental value0.35V[9]
Variation of internal photo voltage as a function of incident optical power with the device parameters in
[7, 24] is also shown in Fig 2 (a) (solid line) along with the experimental results of [24]. The value of reverse
saturation current density at channel-substrate junction was estimated from [24]. It is observed that the nature is
very much similar to that of external photo voltage. Larger photo absorption region in the substrate and a small
reverse saturation current at channel-substrate junction makes internal photo voltage larger than external photo
voltage for a given input power. The variation of photoconductive current with input optical power is depicted
in Fig.2 (b) for V 3.5V and V 1V
ds gs
Various parameters used in this calculation are taken from [7]. As the input power increases, depletion
widths of both front and back depletion regions decrease resulting in larger photoconductive current.
Photoconductive current is typically in micro-sub micro ampere range as evident from Fig 2 (b).
81
15. MATLAB Based Static I-V Characteristics Of Optically Controlled Gaas MESFET’s
Fig. 2.Variation of (a) external, internal photo voltage as a function of optical power,
(b) Photoconductive current as a function of incident Optical power.
Fig. 3. Ids-Vds characteristics of Gaas MESFET without including DLT (dashed line) and
Including DLT with a concentration of NEL2 = 1x1022 m-3 (solid line).
Fig.4. characteristics of Gaas MESFET under optically controlled and backgating conditions.
Fig.3.4.5.6 (waiting)
Since new expressions for I-V characteristics have been derived including deep level traps in the
substrate and backgating with and without illumination, it is necessary to check validity of the above-modeled
82
16. MATLAB Based Static I-V Characteristics Of Optically Controlled Gaas MESFET’s
-V I
expressions. To show how deep level traps in the substrate affect channel current, we simulated ds ds
V 0V
characteristics without DLT (Deep Level Traps) and with DLT for gs under dark condition and are
shown in Fig 3. We validated our model with the results of numerical simulation by Son et al. [18]. It is
observed that presence of DLT with concentration 1x1022 /m3 degrades drain-source current severely. In order
to investigate the effect of backgate voltage on the front depletion region,
0.05 0.051
. A good matching is observed between the two results for 1 and 2 . Once 1 and 2
are extracted, front depletion width can be accordingly modified. Calculated dependence of backgate voltage on
normalized drain-source current in saturation.
Drain-source current of GaAs MESFET under optically controlled conditions in both linear and
saturation region is shown in Fig 4. Different parameters used in our model are taken from [7]. Modeled drain-
source current closely tracks experimental results of [7] under dark and illuminated conditions particularly in
saturation region of device operation. One can achieve better matching in linear region using a complicated
velocity-field relationship rather than a simple two region model. Finite slope of I-V characteristics in saturation
region is explained with the help of channel length modulation (previous models fail to account for the finite
output conductance in saturation region). The effect of backgating on I-V characteristics under dark condition is
also shown in the same figure. Backgate voltage greater than certain threshold voltage (V ) modulates both
thbg
depletion regions thereby reducing the drain current. A substantial increase in drain current due to illumination
is observed in Fig 4. Under illuminated condition of the device excess carriers in front and back depletion
regions develop photo-voltages across these depletion regions which reduce respective depletion widths thereby
increasing the drain-source current. Comparing Fig 2(b) and Fig 4, photoconductive current is much smaller
than the total drain-source current by several orders of magnitude. Finally, photo effects on intrinsic small signal
parameters of GaAs MESFET such as transconductance and output resistance are simulated and shown in Fig 5
along with backgating and DLT effects. It was observed again that presence of DLT in substrate reduces
transconductance and increases output resistance particularly near threshold voltages. Backgate voltage further
reduces transconductance and increases output resistance. But when the device is illuminated both photovoltaic
and photoconductive effects increases transconductance and decreases output resistance
83
17. MATLAB Based Static I-V Characteristics Of Optically Controlled Gaas MESFET’s
.
Fig. 5.Transconductance and output resistance of Gaas MESFET under dark, illuminated and backgating
conditions. Deviation in transconductance and output resistance without considering DLT (ideal case), with
DLT (real case) is also depicted. Various parameters in this calculation are taken from [7].
IV. CONCLUSIONS
A new and systematic way of modeling photo effects on the static I-V characteristics of GaAs
MESFET’s in both linear and saturation regions is presented. Effect of illumination on the device is explained in
terms of photovoltaic and photoconductive effects. Photoconductive current is shown to be small by several
orders of magnitude than total drain-source current. Reduction of drain-source current due to deep level traps in
the substrate is explained analytically under optically controlled conditions of GaAs MESFET for the first time.
Finite slope in the I-V characteristics in saturation region of GaAs MESFET is modeled with the help of channel
length modulation. Further, effect of backgating is also included in modeling I-V characteristics. Finally, small
signal parameters of MESFET such as transconductance and output resistance are derived from the modeled I-V
characteristics. The theoretical conclusions are complemented by comparing with reported experimental results
in the literature, which conform the theory. Since accurate dc modeling is key to accurate ac modeling,this
model may be very useful for the designing of GaAs MESFET’s particularly in MMIC’s and OEIC’s.
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