The document discusses MOSFET theory and operation, including:
- MOSFET device structure and types (depletion and enhancement mode).
- Regions of operation depending on gate-source and drain-source voltages.
- Effects that occur at small device geometries including short channel effects like drain-induced barrier lowering, velocity saturation, and hot carriers.
- Operation and efficiency of solar cells made from semiconductor materials, and how efficiency depends on the material bandgap. Design improvements like PERL cells are also discussed.
Reduced channel length cause departures from long channel behaviour as two-dimensional potential distribution and high electric fields give birth to Short channel effects.
Here are the all short channel effects that you require.It consist of:-
Drain Induced Barrier Lowering
Hot electron Effect
Impact Ionization
Surface Scattering
Velocity saturation
Reduced channel length cause departures from long channel behaviour as two-dimensional potential distribution and high electric fields give birth to Short channel effects.
Here are the all short channel effects that you require.It consist of:-
Drain Induced Barrier Lowering
Hot electron Effect
Impact Ionization
Surface Scattering
Velocity saturation
Short Channel Effects are governed by complex physical phenomena and mainly Influenced because of both vertical and horizontal electric field components.
To meet the current requirements of
Electronic devices, the miniaturization of devices is important. And so is Second Order effects which otherwise degrade the performance of devices.
Microelectronic technology
This report briefly discusses the need for Metal-Oxide-Semiconductor Field Effect Transistors (MOSFETs), their structure and principle of operation. Then it details the fabrication and characterization of the MOSFETs fabricated at the microelectronic lab at University of Malaya
shows the simulation and analysis of a MOSFET device using the MOSFet tool. Several powerful analytic features of this tool are demonstrated, including the following:
calculation of Id-Vg curves
potential contour plots along the device at equilibrium and at the final applied bias
electron density contour plots along the device at equilibrium and at the final applied bias
spatial doping profile along the device
1D spatial potential profile along the device
SHORT-CHANNEL EFFECTS
A MOSFET is considered to be short when the channel length ‘L’ is the same order of magnitude as the depletion-layer widths (xdD, xdS). The potential distribution in the channel now depends upon both, transverse field Ex, due to gate bias and also on the longitudinal field Ey, due to drain bias When the Gate channel length <<1 m, short channel effect becomes important .
This leads to many
undesirable effects in MOSFET.
The short-channel effects are attributed to two physical phenomena:
A) The limitation imposed on electron drift characteristics in the channel,
B) The modification of the threshold voltage due to the shortening channel length.
In particular five different short-channel effects can be distinguished:
1. Drain-induced barrier lowering and “Punch through”
2. Surface scattering
3. Velocity saturation
4. Impact ionization
5. Hot electrons
Short Channel Effects are governed by complex physical phenomena and mainly Influenced because of both vertical and horizontal electric field components.
To meet the current requirements of
Electronic devices, the miniaturization of devices is important. And so is Second Order effects which otherwise degrade the performance of devices.
Threshold Voltage & Channel Length ModulationBulbul Brahma
Design and Technology of Electronic Devices:
Review of microelectronic devices, introduction to MOS technology and related devices.
MOS transistor theory, scaling theory related to MOS circuits, short channel effect and its
consequences, narrow width effect, FN tunnelling, Double gate MOSFET, Cylindrical
MOSFET, Basic concept of CMOS circuits and logic design. Circuit characterization and
performance estimation, important issues in real devices. PE logic, Domino logic, Pseudo
N-MOS logic-dynamic CMOS and Clocking, layout design and stick diagram, CMOS
analog circuit design, CMOS design methods. Introduction to SOI, Multi layer circuit
design and 3D integration. CMOS processing technology: Crystal grown and Epitaxy, Film
formation, Lithography and Etching, Impurity doping, Integrated Devices.
Threshold voltage roll-off for sub-10 nm asymmetric double gate MOSFETIJECEIAES
Threshold voltage roll-off is analyzed for sub-10 nm asymmetric double gate (DG) MOSFET. Even asymmetric DGMOSFET will increase threshold voltage roll-off in sub-10 nm channel length because of short channel effects due to the increase of tunneling current, and this is an obstacle against the miniaturization of asymmetric DGMOSFET. Since asymmetric DGMOSFET can be produced differently in top and bottom oxide thickness, top and bottom oxide thicknesses will affect the threshold voltage roll-off. To analyze this, thermal emission current and tunneling current have been calculated, and threshold voltage roll-off by the reduction of channel length has been analyzed by using channel thickness and top/bottom oxide thickness as parameters. As a result, it is found that, in short channel asymmetric double gate MOSFET, threshold voltage roll-off is changed greatly according to top/bottom gate oxide thickness, and that threshold voltage roll-off is more influenced by silicon thickness. In addition, it is found that top and bottom oxide thickness have a relation of inverse proportion mutually for maintaining identical threshold voltage. Therefore, it is possible to reduce the leakage current of the top gate related with threshold voltage by increasing the thickness of the top gate oxide while maintaining the same threshold voltage.
In electronics, short-channel effects occur in MOSFETs in which the channel length is comparable to the depletion layer widths of the source and drain junctions. These effects include, in particular, drain-induced barrier lowering, velocity saturation, Quantum confinement and hot carrier degradation
Short Channel Effects are governed by complex physical phenomena and mainly Influenced because of both vertical and horizontal electric field components.
To meet the current requirements of
Electronic devices, the miniaturization of devices is important. And so is Second Order effects which otherwise degrade the performance of devices.
Microelectronic technology
This report briefly discusses the need for Metal-Oxide-Semiconductor Field Effect Transistors (MOSFETs), their structure and principle of operation. Then it details the fabrication and characterization of the MOSFETs fabricated at the microelectronic lab at University of Malaya
shows the simulation and analysis of a MOSFET device using the MOSFet tool. Several powerful analytic features of this tool are demonstrated, including the following:
calculation of Id-Vg curves
potential contour plots along the device at equilibrium and at the final applied bias
electron density contour plots along the device at equilibrium and at the final applied bias
spatial doping profile along the device
1D spatial potential profile along the device
SHORT-CHANNEL EFFECTS
A MOSFET is considered to be short when the channel length ‘L’ is the same order of magnitude as the depletion-layer widths (xdD, xdS). The potential distribution in the channel now depends upon both, transverse field Ex, due to gate bias and also on the longitudinal field Ey, due to drain bias When the Gate channel length <<1 m, short channel effect becomes important .
This leads to many
undesirable effects in MOSFET.
The short-channel effects are attributed to two physical phenomena:
A) The limitation imposed on electron drift characteristics in the channel,
B) The modification of the threshold voltage due to the shortening channel length.
In particular five different short-channel effects can be distinguished:
1. Drain-induced barrier lowering and “Punch through”
2. Surface scattering
3. Velocity saturation
4. Impact ionization
5. Hot electrons
Short Channel Effects are governed by complex physical phenomena and mainly Influenced because of both vertical and horizontal electric field components.
To meet the current requirements of
Electronic devices, the miniaturization of devices is important. And so is Second Order effects which otherwise degrade the performance of devices.
Threshold Voltage & Channel Length ModulationBulbul Brahma
Design and Technology of Electronic Devices:
Review of microelectronic devices, introduction to MOS technology and related devices.
MOS transistor theory, scaling theory related to MOS circuits, short channel effect and its
consequences, narrow width effect, FN tunnelling, Double gate MOSFET, Cylindrical
MOSFET, Basic concept of CMOS circuits and logic design. Circuit characterization and
performance estimation, important issues in real devices. PE logic, Domino logic, Pseudo
N-MOS logic-dynamic CMOS and Clocking, layout design and stick diagram, CMOS
analog circuit design, CMOS design methods. Introduction to SOI, Multi layer circuit
design and 3D integration. CMOS processing technology: Crystal grown and Epitaxy, Film
formation, Lithography and Etching, Impurity doping, Integrated Devices.
Threshold voltage roll-off for sub-10 nm asymmetric double gate MOSFETIJECEIAES
Threshold voltage roll-off is analyzed for sub-10 nm asymmetric double gate (DG) MOSFET. Even asymmetric DGMOSFET will increase threshold voltage roll-off in sub-10 nm channel length because of short channel effects due to the increase of tunneling current, and this is an obstacle against the miniaturization of asymmetric DGMOSFET. Since asymmetric DGMOSFET can be produced differently in top and bottom oxide thickness, top and bottom oxide thicknesses will affect the threshold voltage roll-off. To analyze this, thermal emission current and tunneling current have been calculated, and threshold voltage roll-off by the reduction of channel length has been analyzed by using channel thickness and top/bottom oxide thickness as parameters. As a result, it is found that, in short channel asymmetric double gate MOSFET, threshold voltage roll-off is changed greatly according to top/bottom gate oxide thickness, and that threshold voltage roll-off is more influenced by silicon thickness. In addition, it is found that top and bottom oxide thickness have a relation of inverse proportion mutually for maintaining identical threshold voltage. Therefore, it is possible to reduce the leakage current of the top gate related with threshold voltage by increasing the thickness of the top gate oxide while maintaining the same threshold voltage.
In electronics, short-channel effects occur in MOSFETs in which the channel length is comparable to the depletion layer widths of the source and drain junctions. These effects include, in particular, drain-induced barrier lowering, velocity saturation, Quantum confinement and hot carrier degradation
DESIGN OF DIFFERENT DIGITAL CIRCUITS USING SINGLE ELECTRON DEVICESmsejjournal
Single Electron transistor (SET) is foreseen as an excellently growing technology. The aim of this paper is
to present in short the fundamentals of SET as well as to realize its application in the design of single
electron device based novel digital logic circuits with the help of a Monte Carlo based simulator. A Single
Electron Transistors (SET) is characterized by two most substantial determinants. One is very low power
dissipation while the other is its small stature that makes it a favorable suitor for the future generation of
very high level integration. With the utilization of SET, technology is moving past CMOS age resulting in
power efficient, high integrity, handy and high speed devices. Conducting a check on the transport of single
electrons is one of the most stirring aspects of SET technologies. Apparently, Monte Carlo technique is in
vogue in terms of simulating SED based circuits. Hence, a MC based tool called SIMON 2.0 is exercised
upon for the design and simulation of these digital logic circuits. Further, an efficient functioning of the
logic circuits such as multiplexers, decoders, adders and converters are illustrated and established by
means of circuit simulation using SIMON 2.0 simulator.
DESIGN OF DIFFERENT DIGITAL CIRCUITS USING SINGLE ELECTRON DEVICESmsejjournal
Single Electron transistor (SET) is foreseen as an excellently growing technology. The aim of this paper is
to present in short the fundamentals of SET as well as to realize its application in the design of single
electron device based novel digital logic circuits with the help of a Monte Carlo based simulator. A Single
Electron Transistors (SET) is characterized by two most substantial determinants. One is very low power
dissipation while the other is its small stature that makes it a favorable suitor for the future generation of
very high level integration. With the utilization of SET, technology is moving past CMOS age resulting in
power efficient, high integrity, handy and high speed devices. Conducting a check on the transport of single
electrons is one of the most stirring aspects of SET technologies. Apparently, Monte Carlo technique is in
vogue in terms of simulating SED based circuits. Hence, a MC based tool called SIMON 2.0 is exercised
upon for the design and simulation of these digital logic circuits. Further, an efficient functioning of the
logic circuits such as multiplexers, decoders, adders and converters are illustrated and established by
means of circuit simulation using SIMON 2.0 simulator.
This presentation is for beginners of electronics. This will give you a brief about all the important basic building blocks of electronics and hence will be helpful in creating a good foundation.
Single elctron transistor PHASE 1.pptxssuser1580e5
PART-01
Single electron devices (SEDs) are the promising candidates where the bits can be defined using only a few electrons, leading to circuits with immunity from statistical fluctuations in the number of electrons per bit and very low power consumption
Analytical modeling of electric field distribution in dual material junctionl...VLSICS Design
In this paper, electric field distribution of the junctionless dual material surrounding gate MOSFETs
(JLDMSG) is developed. Junctionless is a device that has similar characteristics like junction based
devices, but junctionless has a positive flatband voltage with zero electric field. In Surrounding gate
MOSFETs gate material surrounds the channel in all direction , therefore it can overcome the short
channel effects effectively than other devices. In this paper, surface potential and electric field distribution
is modelled. The proposed surface potential model is compared with the existing central potential model. It
is observed that the short channel effects (SCE) is reduced and the performance is better than the existing
method.
Industrial Training at Shahjalal Fertilizer Company Limited (SFCL)MdTanvirMahtab2
This presentation is about the working procedure of Shahjalal Fertilizer Company Limited (SFCL). A Govt. owned Company of Bangladesh Chemical Industries Corporation under Ministry of Industries.
Water scarcity is the lack of fresh water resources to meet the standard water demand. There are two type of water scarcity. One is physical. The other is economic water scarcity.
Event Management System Vb Net Project Report.pdfKamal Acharya
In present era, the scopes of information technology growing with a very fast .We do not see any are untouched from this industry. The scope of information technology has become wider includes: Business and industry. Household Business, Communication, Education, Entertainment, Science, Medicine, Engineering, Distance Learning, Weather Forecasting. Carrier Searching and so on.
My project named “Event Management System” is software that store and maintained all events coordinated in college. It also helpful to print related reports. My project will help to record the events coordinated by faculties with their Name, Event subject, date & details in an efficient & effective ways.
In my system we have to make a system by which a user can record all events coordinated by a particular faculty. In our proposed system some more featured are added which differs it from the existing system such as security.
Explore the innovative world of trenchless pipe repair with our comprehensive guide, "The Benefits and Techniques of Trenchless Pipe Repair." This document delves into the modern methods of repairing underground pipes without the need for extensive excavation, highlighting the numerous advantages and the latest techniques used in the industry.
Learn about the cost savings, reduced environmental impact, and minimal disruption associated with trenchless technology. Discover detailed explanations of popular techniques such as pipe bursting, cured-in-place pipe (CIPP) lining, and directional drilling. Understand how these methods can be applied to various types of infrastructure, from residential plumbing to large-scale municipal systems.
Ideal for homeowners, contractors, engineers, and anyone interested in modern plumbing solutions, this guide provides valuable insights into why trenchless pipe repair is becoming the preferred choice for pipe rehabilitation. Stay informed about the latest advancements and best practices in the field.
Final project report on grocery store management system..pdfKamal Acharya
In today’s fast-changing business environment, it’s extremely important to be able to respond to client needs in the most effective and timely manner. If your customers wish to see your business online and have instant access to your products or services.
Online Grocery Store is an e-commerce website, which retails various grocery products. This project allows viewing various products available enables registered users to purchase desired products instantly using Paytm, UPI payment processor (Instant Pay) and also can place order by using Cash on Delivery (Pay Later) option. This project provides an easy access to Administrators and Managers to view orders placed using Pay Later and Instant Pay options.
In order to develop an e-commerce website, a number of Technologies must be studied and understood. These include multi-tiered architecture, server and client-side scripting techniques, implementation technologies, programming language (such as PHP, HTML, CSS, JavaScript) and MySQL relational databases. This is a project with the objective to develop a basic website where a consumer is provided with a shopping cart website and also to know about the technologies used to develop such a website.
This document will discuss each of the underlying technologies to create and implement an e- commerce website.
Sachpazis:Terzaghi Bearing Capacity Estimation in simple terms with Calculati...Dr.Costas Sachpazis
Terzaghi's soil bearing capacity theory, developed by Karl Terzaghi, is a fundamental principle in geotechnical engineering used to determine the bearing capacity of shallow foundations. This theory provides a method to calculate the ultimate bearing capacity of soil, which is the maximum load per unit area that the soil can support without undergoing shear failure. The Calculation HTML Code included.
COLLEGE BUS MANAGEMENT SYSTEM PROJECT REPORT.pdfKamal Acharya
The College Bus Management system is completely developed by Visual Basic .NET Version. The application is connect with most secured database language MS SQL Server. The application is develop by using best combination of front-end and back-end languages. The application is totally design like flat user interface. This flat user interface is more attractive user interface in 2017. The application is gives more important to the system functionality. The application is to manage the student’s details, driver’s details, bus details, bus route details, bus fees details and more. The application has only one unit for admin. The admin can manage the entire application. The admin can login into the application by using username and password of the admin. The application is develop for big and small colleges. It is more user friendly for non-computer person. Even they can easily learn how to manage the application within hours. The application is more secure by the admin. The system will give an effective output for the VB.Net and SQL Server given as input to the system. The compiled java program given as input to the system, after scanning the program will generate different reports. The application generates the report for users. The admin can view and download the report of the data. The application deliver the excel format reports. Because, excel formatted reports is very easy to understand the income and expense of the college bus. This application is mainly develop for windows operating system users. In 2017, 73% of people enterprises are using windows operating system. So the application will easily install for all the windows operating system users. The application-developed size is very low. The application consumes very low space in disk. Therefore, the user can allocate very minimum local disk space for this application.
Hybrid optimization of pumped hydro system and solar- Engr. Abdul-Azeez.pdffxintegritypublishin
Advancements in technology unveil a myriad of electrical and electronic breakthroughs geared towards efficiently harnessing limited resources to meet human energy demands. The optimization of hybrid solar PV panels and pumped hydro energy supply systems plays a pivotal role in utilizing natural resources effectively. This initiative not only benefits humanity but also fosters environmental sustainability. The study investigated the design optimization of these hybrid systems, focusing on understanding solar radiation patterns, identifying geographical influences on solar radiation, formulating a mathematical model for system optimization, and determining the optimal configuration of PV panels and pumped hydro storage. Through a comparative analysis approach and eight weeks of data collection, the study addressed key research questions related to solar radiation patterns and optimal system design. The findings highlighted regions with heightened solar radiation levels, showcasing substantial potential for power generation and emphasizing the system's efficiency. Optimizing system design significantly boosted power generation, promoted renewable energy utilization, and enhanced energy storage capacity. The study underscored the benefits of optimizing hybrid solar PV panels and pumped hydro energy supply systems for sustainable energy usage. Optimizing the design of solar PV panels and pumped hydro energy supply systems as examined across diverse climatic conditions in a developing country, not only enhances power generation but also improves the integration of renewable energy sources and boosts energy storage capacities, particularly beneficial for less economically prosperous regions. Additionally, the study provides valuable insights for advancing energy research in economically viable areas. Recommendations included conducting site-specific assessments, utilizing advanced modeling tools, implementing regular maintenance protocols, and enhancing communication among system components.
Student information management system project report ii.pdfKamal Acharya
Our project explains about the student management. This project mainly explains the various actions related to student details. This project shows some ease in adding, editing and deleting the student details. It also provides a less time consuming process for viewing, adding, editing and deleting the marks of the students.
About
Indigenized remote control interface card suitable for MAFI system CCR equipment. Compatible for IDM8000 CCR. Backplane mounted serial and TCP/Ethernet communication module for CCR remote access. IDM 8000 CCR remote control on serial and TCP protocol.
• Remote control: Parallel or serial interface.
• Compatible with MAFI CCR system.
• Compatible with IDM8000 CCR.
• Compatible with Backplane mount serial communication.
• Compatible with commercial and Defence aviation CCR system.
• Remote control system for accessing CCR and allied system over serial or TCP.
• Indigenized local Support/presence in India.
• Easy in configuration using DIP switches.
Technical Specifications
Indigenized remote control interface card suitable for MAFI system CCR equipment. Compatible for IDM8000 CCR. Backplane mounted serial and TCP/Ethernet communication module for CCR remote access. IDM 8000 CCR remote control on serial and TCP protocol.
Key Features
Indigenized remote control interface card suitable for MAFI system CCR equipment. Compatible for IDM8000 CCR. Backplane mounted serial and TCP/Ethernet communication module for CCR remote access. IDM 8000 CCR remote control on serial and TCP protocol.
• Remote control: Parallel or serial interface
• Compatible with MAFI CCR system
• Copatiable with IDM8000 CCR
• Compatible with Backplane mount serial communication.
• Compatible with commercial and Defence aviation CCR system.
• Remote control system for accessing CCR and allied system over serial or TCP.
• Indigenized local Support/presence in India.
Application
• Remote control: Parallel or serial interface.
• Compatible with MAFI CCR system.
• Compatible with IDM8000 CCR.
• Compatible with Backplane mount serial communication.
• Compatible with commercial and Defence aviation CCR system.
• Remote control system for accessing CCR and allied system over serial or TCP.
• Indigenized local Support/presence in India.
• Easy in configuration using DIP switches.
Saudi Arabia stands as a titan in the global energy landscape, renowned for its abundant oil and gas resources. It's the largest exporter of petroleum and holds some of the world's most significant reserves. Let's delve into the top 10 oil and gas projects shaping Saudi Arabia's energy future in 2024.
Top 10 Oil and Gas Projects in Saudi Arabia 2024.pdf
small geometry effect and working of solar cell
1. ECS-504
DIGITAL CIRCUITS AND SYSTEMS
Shivank Rastogi
18BEC022
BTECH-ECE 5TH SEMESTER
Faculty of Engineering&Technology
Jamia Millia Islamia, New Delhi
2. MOSFET THEORY Small Geometry Effect Solar Cell
• MOSFET stands for Metal Oxide Silicon Field Effect Transistor or
Metal Oxide Semiconductor Field Effect Transistor.
• MOSFET is a 4 terminal device with Terminal source, Drain, Gate
and Body
• Source and Body are generally connected together
• The Gate potential controls the formation of channel
• MOSFETs are available in two basic forms:
Depletion Type – the transistor requires the Gate-Source
voltage, ( VGS ) to switch the device “OFF”. The depletion mode
MOSFET is equivalent to a “Normally Closed” switch.
Enhancement Type– the transistor requires a Gate-Source voltage,
( VGS ) to switch the device “ON”. The enhancement mode MOSFET is
equivalent to a “Normally Open” switch.
3. MOSFET THEORY Small Geometry Effect Solar Cell
Depletion-Mode MOSFET:
The depletion type MOSFET transistor is equivalent to
a “normally closed” switch. The depletion type of
transistors requires gate – source voltage (VGS) to
switch OFF the device.
Enhancement-Mode MOSFET:
The Enhancement ode MOSFET is equivalent to
“Normally Open” switch and these types of
transistors require gate-source voltage to switch
ON the device.
4. MOSFET THEORY Small Geometry Effect Solar Cell
• Four basic types of MOSFETs-cross sections at V G = 0 V, output and transfer characteristics
5. In MOSFET we have various regions of
operation
By varying V-
GS
By varying V-DS
Under linear distribution
of charge
Accumulation region, VG < 0
Depletion/Weak Inversion region,
VG > 0
Strong Inversion region, VG >>0
Linear/Triode region, VDS < (VGS-
VTH)
Saturation region, VDS > (VGS-
VTH)
Under Linear region:
ID
CO X W (VGS VTH)VD
L
Resistance
R : (VGS VTH)
R 1/
Transconductance:
OX
L
C W
Under Saturation region: (can act as current
source)
2L
CO X W (VGS VTH )2
ID, sat
Transconductan
ce
dVG L
dID
COXW (VGS VTH )
g m ,sat
dI
dVG L
C WV
gm,lin D
O X D
Triode
Mode
MOSFET THEORY Small Geometry Effect Solar Cell
CCharacteristics and Region of
Operation
6. MOSFET THEORY Short Geometry Effect Solar Cell
Channel Length
• The channel length is a very critical parameter in CMOS
technology for performance projection, device design, modeling
and circuit simulation of MOSFETs
• The so-called channel length is a broad description ofthree
different channel lengths in the MOSFET. One is the mask
channel length Lm, which denotes the physical length ofthe gate
mask. Another is the electrical effective channel length LetT'
which defines the length ofa region near the Sj-Sj02 interface in
which the inversion free-carrier density is controlled by the gate
voltage. The channel length is given by:
Del Leff is the effective channel length reduction
etT is the effective channel length reduction
• The third channel length used frequently is the
metallurgical channel length Lmet, which is the
distance between the source and drain
metallurgical junctions at the SjS;02 interface
7. MOSFET THEORY Short Geometry Effect Solar Cell
Channel Length Modulation and Pinch off :
8. MOSFET THEORY Short Geometry Effect Solar Cell
Short Channel Effect :
• A MOSFET device is considered to be short when the channel length is the
same order of magnitude as the depletion-layer widths (xdD, xdS) of the
source and drain junction. As the channel length L is reduced to increase
both the operation speed and the number of components per chip, the so-
called short-channel effects arise.
9. MOSFET THEORY Short Geometry Effect Solar Cell
Short Channel Effect:
• A MOSFET is considered to be short when the channel length ‘L’ is the same order of magnitude as the
depletion-layer widths (xdD, xdS). The potential distribution in the channel now depends upon both,
transverse field Ex, due to gate bias and also on the longitudinal field Ey, due to drain bias When the Gate
channel length <<1 m, short channel effect becomes important . This leads to many undesirable effects in
MOSFET.
The short-channel effects are attributed to two physical phenomena:
1. the limitation imposed on electron drift characteristics in the channel,
2. the modification of the threshold voltage due to the shortening channel length.
In particular five different short-channel effects can be distinguished:
1. surface scattering
2. drain-induced barrier lowering and punchthrough
3.velocity saturation
4.impact ionization
5.hot electrons
10. MOSFET THEORY Short Geometry Effect Solar Cell
Drain-induced barrier lowering and punchthrough:
When the depletion regions surrounding the drain extends to
the source, so that the two depletion layer merge (i.e., when
xdS + xdD = L), punchtrough occurs. Punchthrough can be
minimized with thinner oxides, larger substrate doping,
shallower junctions, and obviously with longer channels. The
current flow in the channel depends on creating and sustaining
an inversion layer on the surface. If the gate bias voltage is not
sufficient to invert the surface (VGSthe carriers (electrons) in
the channel face a potential barrier that blocks the flow.
Increasing the gate voltage reduces this potential barrier and,
eventually, allows the flow of carriers under the influence of
the channel electric field. In small-geometry MOSFETs, the
potential barrier is controlled by both the gate-to-source
voltage VGS and the drain-to-source voltage VDS. If the drain
voltage is increased, the potential barrier in the channel
decreases, leading to drain-induced barrier lowering (DIBL).
The reduction of the potential barrier eventually allows
electron flow between the source and the drain, even if the
gate-to-source voltage is lower than the threshold voltage. The
channel current that flows under this conditions (VGS<Vto) is
called sum threshold current
11. MOSFET THEORY Short Geometry Effect Solar Cell
SURFACE SCATTERING: • For small-geometry MOSFETs, the electrons
mobility in the channel depends on a two-
dimensional electric field (Ex, Ey). The surface
scattering occurs when electrons are accelerated
toward the surface by the vertical component of
the electric field Ex
• As the channel length becomes smaller due to the
lateral extension of the depletion layer into the
channel region, the longitudinal electric field
component Ey increases, and the surface mobility
becomes field-dependent. Since the carrier
transport in a MOSFET is confined within the
narrowinversion layer, and the surface scattering
(that is the collisions suffered by the electrons
that are accelerated toward the interface by ex)
causes reduction of the mobility, the electrons
move with great difficulty parallel to the
interface, so that the average surface mobility,
even for small values of Ey, is about half as much
as that of the bulk mobility.
12. MOSFET THEORY Short Geometry Effect Solar Cell
Velocity Saturation:
• The electron velocity is related to the electric
field through the mobility: V= μE
• For higher fields the velocity does not increase with electric field, we have degradation of mobility because of
scattering by vertical field. This leads to earlier saturation of current. i.e.,before VGS-VTH. Net result is
reduction in drain current .
• The velocity saturation reduces the transconductance of short-channel devices in the saturation condiction.
13. MOSFET THEORY Short Geometry Effect Solar Cell
IMPACT IONIZATION: The presence of high longitudinal fields can accelerate
electrons that may be able of ionizing Si atoms by impacting
against them
Normally most of the e- are attracted by the drain, so it is
plausible a higher concentration of holes near the source
If the holes concentration on the source is able to creates
a voltage drop on the source-substrate n-p junction of
about 0.6V then
e- may be injected from source to substrate
e- travel toward the drain, increasing their energy and
create new e-h pairs
e- may escape the drain fields and afect other device
They can gain enough energy as they travel toward the
drain to create new eh pairs. The situation can worsen if
some electrons generated due to high fields escape the
drain field to travel into the substrate, thereby affecting
other devices on a chip.
14. MOSFET THEORY Short Geometry Effect Solar Cell
Hot Electrons:
The channel Hot Electrons effect is caused by electrons flowing in the channel for large VDS
e- arriving at the Si-SiO2 interface with enough kinetic energy >3.1ev to surmount the surface potential barrier
are injected into the oxide
This may degrade permanently the C-V characteristics of a MOSFETs
15. MOSFET THEORY Short Geometry Effect Solar Cell
CONCLUSION:
FOR IMPACT IONIZATION
FOR PUNCH THROUGH
Short Channel Effects are governed by
complex physical phenomena and mainly
Influenced because of both vertical and
horizontal electric field components.
To meet the current requirements of
Electronic devices, the miniaturization of
devices is important. And so is Second Order
effects which otherwise degrade the
performance of devices.
16. MOSFET THEORY Short Geometry Effect SOLAR CELLS
INTRODUCTION: • Solar cells and photodetectors are devices that convert
an optical input into current. A solar cell is an example
of a photovoltaic device, i.e, a device that generates
voltage when exposed to light.
• The photovoltaic effect was discovered by Alexander-
Edmond Becquerel in 1839, in a junction formed
between an electrode (platinum) and an electrolyte
(silver chloride).
• The first photovoltaic device was built, using a Si pn
junction, by Russell Ohl in 1939. The functioning of a
solar cell is similar to the photodiode (photodetector). It
is a photodiode that is unbiased and connected to a load
(impedence).
17. MOSFET THEORY Short Geometry Effect SOLAR CELLS
SOLAR SPECTRUM: • The solar spectrum typically extends from the IR to the
UV region, wavelength range from 3 µm to 0.2 µm. But
the intensity is not uniform.
• A typical solar spectrum, as a plot of spectral irradiance
vs. wavelength, is shown in figure .
• The area under the curve gives the total areal intensity
and this is approximately 1.35 kW m−2 .
• The solar spectrum can be approximated by a black
body radiation curve at temperature of approximately
5250 ◦C.
• There is also a difference in the spectra measured at the
top of the atmosphere and at the surface, due to
atmospheric scattering and absorption.
18. MOSFET THEORY Short Geometry Effect SOLAR CELLS
Solar Cell working principle: • A simple solar cell is a pn junction diode.The n
region is heavily doped and thin so that the light can
penetrate through it easily. The p region is lightly
doped so that most of the depletion region lies in the
p side.
• The penetration depends on the wavelength and the
absorption coefficient increases as the wavelength
decreases.
• Electron hole pairs (EHPs) are mainly created in the
depletion region and due to the built-in potential and
electric field, electrons move to the n region and the
holes to the p region. When an external load is
applied, the excess electrons travel through the load
to recombine with the excess holes.
• The shorter wavelengths (higher absorption
coefficient) are absorbed in the n region and the
longer wavelengths are absorbed in the bulk of the p
region
• The total width of the region that contributes to the
solar cell current is wd + Le + Lh, where wd is the
depletion width
Principle of operation of a pn
junction solar cell. Radiation is
absorbed in the depletion region
and produces electrons and holes.
These are separated by the built-in
potential. Depending on the
wavelength and the thickness
different parts of the device can
absorb different regions of the
solar spectrum
19. MOSFET THEORY Short Geometry Effect SOLAR CELLS
Solar Cell Materials and Efficiency:
Solar cell
efficiency as a
function of band
gap of the
semiconductor
material. There is
an particular
band gap range
where the
efficiency is
maximum.
: Si solar cell with an
inverted pyramid
structure to enhance
absorption of the incoming
radiation. These are called
PERL cells. The inverted
pyramid structure causes
multiple reflections at the
surface, which help in
absorption of the incoming
radiation
• The efficiency of the solar cell depends on the band gap
of the material
• Polycrystalline solar cells are cheaper to manufacture
but have a lower efficiency since the microstructure
introduces defects in the material that can trap carriers
• Amorphous solar cells have an even lower efficiency
but can be grown directly on glass substrates by
techniques like sputtering so that the overall cost of
manufacturing is lowered
• There are also design improvements in the solar cell
that can enhance the efficiency. PERL (passivated
emitter rear locally diffused) cells, shown in figure
have an efficiency of 24% due to the inverted pyramid
structure etched on the surface that enhances
absorption.