1) Electrons and holes in semiconductors undergo thermal motion due to collisions with crystal imperfections, with an average time between collisions of 0.1 ps.
2) When an electric field is applied, electrons and holes also drift with mobilities dependent on material properties like doping concentration. Higher mobilities are found in materials like GaAs, desirable for high-speed devices.
3) Electron and hole concentrations can diffuse from higher to lower concentration regions due to gradients in electrochemical potential. Diffusion and drift currents, along with generation and recombination, determine the net carrier transport and distribution in semiconductors.
Ch2 lecture slides Chenming Hu Device for ICChenming Hu
The document summarizes key concepts related to the motion and recombination of electrons and holes in semiconductors. It discusses thermal motion, drift velocity, mobility, diffusion current, and recombination lifetime. Thermal motion causes electrons and holes to zigzag randomly through a semiconductor. An electric field causes drift, where mobility determines the drift velocity. Diffusion current flows from high concentration to low. Recombination lifetime is the time for excess carriers to recombine after generation ceases.
This document summarizes key concepts from a chapter on the motion and recombination of electrons and holes in semiconductors.
[1] Carriers in semiconductors undergo both thermal motion due to temperature as well as drift motion in the presence of an electric field. The drift velocity depends on factors like carrier mobility and the electric field.
[2] Carriers can also diffuse from regions of higher concentration to lower concentration. The diffusion current depends on the diffusion constant which is related to carrier mobility via the Einstein relation.
[3] When carriers recombine, they restore equilibrium conditions by decaying over time with a characteristic lifetime. Recombination involves traps and centers that facilitate the process.
1. The document discusses carrier transport mechanisms in semiconductors including drift, diffusion, and generation-recombination. It explains how mobility, resistivity, and the Einstein relationship relate these concepts.
2. Recombination and generation processes are defined as the annihilation or creation of electron-hole pairs. Various recombination mechanisms such as band-to-band, defect-assisted, and impact ionization are described.
3. Momentum considerations for different carrier transition processes like photon-assisted and phonon-assisted are discussed, noting that photons carry little momentum while phonons carry more momentum.
The document discusses various mechanisms of charge carrier transport in semiconductors including drift and diffusion. It defines carrier drift as the movement of electrons and holes under the influence of an applied electric field. Carrier mobility is introduced as a material property that determines how fast carriers drift in response to an electric field. Diffusion is defined as the movement of carriers from areas of high concentration to low concentration due to random thermal motion. The Einstein relation links diffusion and mobility through the carrier temperature. Total current in a semiconductor is the sum of drift and diffusion currents.
This document contains solutions to physics problems from the 12th CBSE exam. It discusses topics like Lenz's law, electric fields, the photoelectric effect, atomic spectra of hydrogen, rectifiers, and more. The solutions are presented in point form and range from short explanations to longer derivations. Overall, the document provides concise answers and working steps to multiple conceptual and numerical problems in 12th grade physics.
Ch1 lecture slides Chenming Hu Device for IC Chenming Hu
The document discusses the fundamentals of semiconductor materials and devices. It covers topics such as silicon crystal structure, doping, energy bands, carrier concentrations, and the Fermi level. Key points include:
- Silicon crystals have a cubic unit cell structure with each silicon atom bonded to four nearest neighbors. Silicon wafers are cut along specific crystal planes for integrated circuit fabrication.
- Doping silicon with elements from columns III and V of the periodic table creates N-type and P-type materials by introducing extra electrons or holes. This allows the control of carrier concentrations.
- The energy band model describes the transition from discrete atomic energy levels to continuous energy bands in solids. The sizes of the bandgap
1. The document describes a technique to precisely determine the frequency of a ring oscillator using only three parameters: the number of stages (N), the capacitance at each stage (C), and the estimated resistance (R).
2. It derives a formula to calculate the frequency by studying the effects of capacitance on delay, estimating resistance using power dissipation, and applying Barkhausen's criterion for oscillation conditions.
3. The technique was tested using LTspice simulations and was found to estimate frequency accurately irrespective of transistor sizes and technology used.
1. The document describes a technique to precisely determine the frequency of a ring oscillator using only three parameters: the number of stages (N), the capacitance at each stage (C), and the resistance (R).
2. It derives a formula for calculating the frequency by estimating the capacitance (C) through experimentation and the resistance (R) using the power dissipation at a single stage.
3. The technique was tested using LTspice simulations and was shown to estimate frequency accurately across different technologies and transistor dimensions.
Ch2 lecture slides Chenming Hu Device for ICChenming Hu
The document summarizes key concepts related to the motion and recombination of electrons and holes in semiconductors. It discusses thermal motion, drift velocity, mobility, diffusion current, and recombination lifetime. Thermal motion causes electrons and holes to zigzag randomly through a semiconductor. An electric field causes drift, where mobility determines the drift velocity. Diffusion current flows from high concentration to low. Recombination lifetime is the time for excess carriers to recombine after generation ceases.
This document summarizes key concepts from a chapter on the motion and recombination of electrons and holes in semiconductors.
[1] Carriers in semiconductors undergo both thermal motion due to temperature as well as drift motion in the presence of an electric field. The drift velocity depends on factors like carrier mobility and the electric field.
[2] Carriers can also diffuse from regions of higher concentration to lower concentration. The diffusion current depends on the diffusion constant which is related to carrier mobility via the Einstein relation.
[3] When carriers recombine, they restore equilibrium conditions by decaying over time with a characteristic lifetime. Recombination involves traps and centers that facilitate the process.
1. The document discusses carrier transport mechanisms in semiconductors including drift, diffusion, and generation-recombination. It explains how mobility, resistivity, and the Einstein relationship relate these concepts.
2. Recombination and generation processes are defined as the annihilation or creation of electron-hole pairs. Various recombination mechanisms such as band-to-band, defect-assisted, and impact ionization are described.
3. Momentum considerations for different carrier transition processes like photon-assisted and phonon-assisted are discussed, noting that photons carry little momentum while phonons carry more momentum.
The document discusses various mechanisms of charge carrier transport in semiconductors including drift and diffusion. It defines carrier drift as the movement of electrons and holes under the influence of an applied electric field. Carrier mobility is introduced as a material property that determines how fast carriers drift in response to an electric field. Diffusion is defined as the movement of carriers from areas of high concentration to low concentration due to random thermal motion. The Einstein relation links diffusion and mobility through the carrier temperature. Total current in a semiconductor is the sum of drift and diffusion currents.
This document contains solutions to physics problems from the 12th CBSE exam. It discusses topics like Lenz's law, electric fields, the photoelectric effect, atomic spectra of hydrogen, rectifiers, and more. The solutions are presented in point form and range from short explanations to longer derivations. Overall, the document provides concise answers and working steps to multiple conceptual and numerical problems in 12th grade physics.
Ch1 lecture slides Chenming Hu Device for IC Chenming Hu
The document discusses the fundamentals of semiconductor materials and devices. It covers topics such as silicon crystal structure, doping, energy bands, carrier concentrations, and the Fermi level. Key points include:
- Silicon crystals have a cubic unit cell structure with each silicon atom bonded to four nearest neighbors. Silicon wafers are cut along specific crystal planes for integrated circuit fabrication.
- Doping silicon with elements from columns III and V of the periodic table creates N-type and P-type materials by introducing extra electrons or holes. This allows the control of carrier concentrations.
- The energy band model describes the transition from discrete atomic energy levels to continuous energy bands in solids. The sizes of the bandgap
1. The document describes a technique to precisely determine the frequency of a ring oscillator using only three parameters: the number of stages (N), the capacitance at each stage (C), and the estimated resistance (R).
2. It derives a formula to calculate the frequency by studying the effects of capacitance on delay, estimating resistance using power dissipation, and applying Barkhausen's criterion for oscillation conditions.
3. The technique was tested using LTspice simulations and was found to estimate frequency accurately irrespective of transistor sizes and technology used.
1. The document describes a technique to precisely determine the frequency of a ring oscillator using only three parameters: the number of stages (N), the capacitance at each stage (C), and the resistance (R).
2. It derives a formula for calculating the frequency by estimating the capacitance (C) through experimentation and the resistance (R) using the power dissipation at a single stage.
3. The technique was tested using LTspice simulations and was shown to estimate frequency accurately across different technologies and transistor dimensions.
This document describes using active disturbance rejection control (ADRC) for controlling a single-stage photovoltaic system connected to the electrical grid. It compares ADRC to the conventional perturb and observe (P&O) control method. ADRC combined with incremental conductance (ADRC-IC) is used for maximum power point tracking (MPPT) control. ADRC is also used to control the inverter to regulate the DC bus voltage and ensure unity power factor injection into the grid. The system aims to maximize power extraction from the PV array and regulate power injection into the grid with low harmonics.
This document provides instructions for experiments on power semiconductor switches and switch-mode power converters to be carried out by students. The experiments involve testing an SCR using a multimeter, studying the turn-on and turn-off states of an SCR, and effects of gate current. Students will also study the switching parameters of a BJT and build a buck converter circuit. Performance in the experiments, teamwork, and learning attitude will contribute towards marks. Students are advised to read the instructions fully before conducting the experiments.
This document provides a summary of Lecture 2 on electrostatics. It introduces fundamental concepts such as electric charge, Coulomb's law, electric field, electric potential, and the relationship between electric field and electric potential. Continuous distributions of charge such as volume, surface, and line charges are also discussed. Key equations for calculating electric fields and potentials from these various charge distributions are presented.
This paper provides a new approach to reducing high-order harmonics in 400 Hz inverter using a three-level neutral-point clamped (NPC) converter. A voltage control loop using the harmonic compensation combined with NPC clamping diode control technology. The capacitor voltage imbalance also causes harmonics in the output voltage. For 400 Hz inverter, maintain a balanced voltage between the two input (direct current) (DC) capacitors is difficult because the pulse width modulation (PWM) modulation frequency ratio is low compared to the frequency of the output voltage. A method of determining the current flowing into the capacitor to control the voltage on the two balanced capacitors to ensure fast response reversal is also given in this paper. The combination of a high-harmonic resonator controller and a neutral-point voltage controller working together on the 400 Hz NPC inverter structure is given in this paper.
The Carrier Diffusion of a Semiconductorralagaadedayo
1) The lecture discusses carrier diffusion in semiconductors, where particles diffuse from areas of higher concentration to lower concentration. This movement of carriers generates a diffusion current.
2) When an electron density varies in the x-direction in a semiconductor, it results in a net carrier flow and current from left to right. The diffusion coefficient Dn relates the diffusion current density to the concentration gradient.
3) Examples are provided to calculate diffusion current density and excess carrier generation and recombination rates under illumination. Direct generation and recombination of electron-hole pairs is also explained under different conditions.
This document discusses electromagnetic transmission lines and the Smith chart. It introduces equivalent electrical circuit models for coaxial cables, microstrip lines, and twin lead transmission lines using distributed inductors and capacitors. The telegrapher's equations are derived from Kirchhoff's laws. For sinusoidal waves on the transmission lines, phasor analysis is used. Key concepts covered include characteristic impedance, propagation velocity, wavelength, and modeling forward and backward traveling waves.
Physics Sample Paper with General Instruction for Class - 12Learning Three Sixty
Learning 360 brings “Physics sample paper” for CLASS – 12. This document also carries 31 questions with solution of each given question for better understanding of the students. Download for free now; http://www.learning360.net/study_hub/1090-2/
This document describes the design and testing of square, triangular, and sawtooth wave generators using op-amps. It provides the circuit diagrams and operating principles for each type of generator. The square wave generator uses feedback from the output to switch the op-amp between saturation states at a frequency determined by the RC timing components. A triangular wave can be produced by integrating a square wave using another op-amp. Adjusting a potentiometer in the sawtooth generator circuit allows control over the rise and fall times to produce different sawtooth waveforms. The experiment involves building and testing the three generator circuits using 741 op-amps and observing and measuring the output waveforms on an oscilloscope.
EC8252 NOTES 3rd to 5th unit_compressed.pdfkabileshsk2
This document contains a question bank for the course EC8252 - Electronic Devices at Jansons Institute of Technology. It includes 20 multiple choice questions in Part A covering topics like PN junction diodes, diffusion current, drift current, and more. Part B contains 18 numerical and conceptual questions related to PN junction diode characteristics, IV curves, reverse saturation current, and other diode parameters.
The document serves as a study guide for students taking the EC8252 exam, testing their understanding of fundamental electronic device concepts through a variety of questions.
This summary provides the key details about simulation results of a feedback control system to damp electron cloud instabilities in the CERN SPS:
- Simulations using the PIC code WARP modeled a bunch interacting with an electron cloud and the damping effect of a simple feedback system based on a FIR filter.
- With a gain of 0.2, the feedback was able to reduce vertical instabilities and prevent emittance growth for an electron density of 1×1012 m-3.
- Limiting the maximum kick signal led to instability as some slices required more power than could be provided, showing the importance of sufficient amplifier power.
- At a higher electron density of 2×1012 m-3
Basics of semiconductor, current equation, continuity equation, injected mino...Nidhee Bhuwal
This document provides an introduction to semiconductors. It discusses topics such as the crystal structure of germanium and silicon, intrinsic and extrinsic semiconductors, carrier mobility, and diffusion currents. Equations are presented for carrier concentrations, mass action law, drift current density, and the continuity equation. Generation and recombination of charge carriers is explained. Minority carrier injection, potential variation in graded semiconductors, and the contact potential of a step graded junction are also summarized.
Helical Methode - To determine the specific chargeharshadagawali1
1. This experiment aims to determine the specific charge (e/m) of electrons using the helical coil method. A cathode ray tube is placed inside a solenoid and electrons are accelerated towards the screen and deflected by a transverse AC voltage.
2. The resulting motion of the electrons is helical due to the magnetic field produced by the solenoid. By measuring the pitch of the helix, the e/m ratio can be calculated using the given formula.
3. The calculated value of e/m is 1.6 × 1011 C/kg with a percent error of 8.57% compared to the standard value of 1.75 × 1011 C/kg.
The document discusses various computational models for semiconductor device transport simulation. It begins by describing semiclassical transport theory and approaches like drift-diffusion, hydrodynamics, and particle-based Monte Carlo methods. It then covers topics like inclusion of tunneling effects, quantum corrections, and particle-based and quantum transport simulations. Specific models are discussed for generation-recombination mechanisms, low-field and field-dependent mobility, inversion layer mobility, and the hydrodynamic approach for including velocity overshoot effects.
Ch4 lecture slides Chenming Hu Device for ICChenming Hu
The document discusses PN junctions and their properties. It covers:
1) The basic structure of a PN junction and its energy band diagram under equilibrium conditions. A depletion region forms where the bands bend.
2) The built-in potential that exists across the depletion region due to the diffusion of charge carriers. This potential can be calculated from the doping concentrations.
3) The behavior of a PN junction under forward and reverse bias, including how the depletion region width changes with applied voltage. Carrier injection also occurs under forward bias.
4) Breakdown mechanisms that can occur under high reverse bias, including avalanche and tunneling breakdown. Zener diodes are designed to operate
James Clerk Maxwell's equations represent the fundamentals of electricity and magnetism in an elegant and concise form. The document discusses various units used to measure magnetic flux, such as the Maxwell and Weber. It then examines Maxwell's modifications to Ampere's law by including the concept of displacement current to account for changing electric fields producing magnetic fields. As an example, the document calculates the magnetic field produced near a parallel plate capacitor due to the changing electric field between its plates.
The document summarizes research on understanding charge transport in low dimensional semiconductor nanostructures embedded in an insulating matrix. Specifically, it examines current-voltage characteristics of germanium nanowire arrays in an alumina matrix as a function of temperature. Key findings include:
1) At room temperature, conduction follows Ohm's law at low voltages and Mott-Gurney's space charge limited current law at higher voltages.
2) With decreasing temperature, conduction transitions from a trap-free regime to an exponentially distributed trap regime.
3) Mobility decreases with decreasing temperature, and activation energy is extracted from an Arrhenius plot, found to be 85 meV at low temperatures and 301 meV
International Journal of Engineering Research and Development (IJERD)IJERD Editor
journal publishing, how to publish research paper, Call For research paper, international journal, publishing a paper, IJERD, journal of science and technology, how to get a research paper published, publishing a paper, publishing of journal, publishing of research paper, reserach and review articles, IJERD Journal, How to publish your research paper, publish research paper, open access engineering journal, Engineering journal, Mathemetics journal, Physics journal, Chemistry journal, Computer Engineering, Computer Science journal, how to submit your paper, peer reviw journal, indexed journal, reserach and review articles, engineering journal, www.ijerd.com, research journals,
yahoo journals, bing journals, International Journal of Engineering Research and Development, google journals, hard copy of journal
chapter 21Electric charge and electric field.pdfssusercceaa8
The document discusses electric charge and the electric field. It defines electric charge as a fundamental property of matter that can be positive or negative. Benjamin Franklin established that positive charge is possessed by protons and negative charge by electrons. Charges of the same sign repel, while opposite charges attract. Coulomb's law states that the electrostatic force between two point charges is directly proportional to the product of their charges and inversely proportional to the square of the distance between them. The electric field is defined as the electric force on a small test charge divided by that test charge. It is represented by field lines that indicate the direction and strength of the field.
Kinetics of X-ray conductivity for an ideal wide-gap semiconductor irradiated...Andrii Sofiienko
This document discusses the development of a kinetic theory to describe the X-ray conductivity (XRC) of semiconductors and dielectrics when irradiated by X-rays. It begins by outlining the need for such a theory and which characteristics it should describe. It then presents the initial stages of developing the theory, including modeling an ideal semiconductor at low excitation levels and deriving expressions for the spatial distribution of free electrons and holes and their lifetimes. The document also examines how the electric field of free charge carriers affects the distributions as excitation increases and considers incorporating the Coulomb interaction between carriers.
This document describes using active disturbance rejection control (ADRC) for controlling a single-stage photovoltaic system connected to the electrical grid. It compares ADRC to the conventional perturb and observe (P&O) control method. ADRC combined with incremental conductance (ADRC-IC) is used for maximum power point tracking (MPPT) control. ADRC is also used to control the inverter to regulate the DC bus voltage and ensure unity power factor injection into the grid. The system aims to maximize power extraction from the PV array and regulate power injection into the grid with low harmonics.
This document provides instructions for experiments on power semiconductor switches and switch-mode power converters to be carried out by students. The experiments involve testing an SCR using a multimeter, studying the turn-on and turn-off states of an SCR, and effects of gate current. Students will also study the switching parameters of a BJT and build a buck converter circuit. Performance in the experiments, teamwork, and learning attitude will contribute towards marks. Students are advised to read the instructions fully before conducting the experiments.
This document provides a summary of Lecture 2 on electrostatics. It introduces fundamental concepts such as electric charge, Coulomb's law, electric field, electric potential, and the relationship between electric field and electric potential. Continuous distributions of charge such as volume, surface, and line charges are also discussed. Key equations for calculating electric fields and potentials from these various charge distributions are presented.
This paper provides a new approach to reducing high-order harmonics in 400 Hz inverter using a three-level neutral-point clamped (NPC) converter. A voltage control loop using the harmonic compensation combined with NPC clamping diode control technology. The capacitor voltage imbalance also causes harmonics in the output voltage. For 400 Hz inverter, maintain a balanced voltage between the two input (direct current) (DC) capacitors is difficult because the pulse width modulation (PWM) modulation frequency ratio is low compared to the frequency of the output voltage. A method of determining the current flowing into the capacitor to control the voltage on the two balanced capacitors to ensure fast response reversal is also given in this paper. The combination of a high-harmonic resonator controller and a neutral-point voltage controller working together on the 400 Hz NPC inverter structure is given in this paper.
The Carrier Diffusion of a Semiconductorralagaadedayo
1) The lecture discusses carrier diffusion in semiconductors, where particles diffuse from areas of higher concentration to lower concentration. This movement of carriers generates a diffusion current.
2) When an electron density varies in the x-direction in a semiconductor, it results in a net carrier flow and current from left to right. The diffusion coefficient Dn relates the diffusion current density to the concentration gradient.
3) Examples are provided to calculate diffusion current density and excess carrier generation and recombination rates under illumination. Direct generation and recombination of electron-hole pairs is also explained under different conditions.
This document discusses electromagnetic transmission lines and the Smith chart. It introduces equivalent electrical circuit models for coaxial cables, microstrip lines, and twin lead transmission lines using distributed inductors and capacitors. The telegrapher's equations are derived from Kirchhoff's laws. For sinusoidal waves on the transmission lines, phasor analysis is used. Key concepts covered include characteristic impedance, propagation velocity, wavelength, and modeling forward and backward traveling waves.
Physics Sample Paper with General Instruction for Class - 12Learning Three Sixty
Learning 360 brings “Physics sample paper” for CLASS – 12. This document also carries 31 questions with solution of each given question for better understanding of the students. Download for free now; http://www.learning360.net/study_hub/1090-2/
This document describes the design and testing of square, triangular, and sawtooth wave generators using op-amps. It provides the circuit diagrams and operating principles for each type of generator. The square wave generator uses feedback from the output to switch the op-amp between saturation states at a frequency determined by the RC timing components. A triangular wave can be produced by integrating a square wave using another op-amp. Adjusting a potentiometer in the sawtooth generator circuit allows control over the rise and fall times to produce different sawtooth waveforms. The experiment involves building and testing the three generator circuits using 741 op-amps and observing and measuring the output waveforms on an oscilloscope.
EC8252 NOTES 3rd to 5th unit_compressed.pdfkabileshsk2
This document contains a question bank for the course EC8252 - Electronic Devices at Jansons Institute of Technology. It includes 20 multiple choice questions in Part A covering topics like PN junction diodes, diffusion current, drift current, and more. Part B contains 18 numerical and conceptual questions related to PN junction diode characteristics, IV curves, reverse saturation current, and other diode parameters.
The document serves as a study guide for students taking the EC8252 exam, testing their understanding of fundamental electronic device concepts through a variety of questions.
This summary provides the key details about simulation results of a feedback control system to damp electron cloud instabilities in the CERN SPS:
- Simulations using the PIC code WARP modeled a bunch interacting with an electron cloud and the damping effect of a simple feedback system based on a FIR filter.
- With a gain of 0.2, the feedback was able to reduce vertical instabilities and prevent emittance growth for an electron density of 1×1012 m-3.
- Limiting the maximum kick signal led to instability as some slices required more power than could be provided, showing the importance of sufficient amplifier power.
- At a higher electron density of 2×1012 m-3
Basics of semiconductor, current equation, continuity equation, injected mino...Nidhee Bhuwal
This document provides an introduction to semiconductors. It discusses topics such as the crystal structure of germanium and silicon, intrinsic and extrinsic semiconductors, carrier mobility, and diffusion currents. Equations are presented for carrier concentrations, mass action law, drift current density, and the continuity equation. Generation and recombination of charge carriers is explained. Minority carrier injection, potential variation in graded semiconductors, and the contact potential of a step graded junction are also summarized.
Helical Methode - To determine the specific chargeharshadagawali1
1. This experiment aims to determine the specific charge (e/m) of electrons using the helical coil method. A cathode ray tube is placed inside a solenoid and electrons are accelerated towards the screen and deflected by a transverse AC voltage.
2. The resulting motion of the electrons is helical due to the magnetic field produced by the solenoid. By measuring the pitch of the helix, the e/m ratio can be calculated using the given formula.
3. The calculated value of e/m is 1.6 × 1011 C/kg with a percent error of 8.57% compared to the standard value of 1.75 × 1011 C/kg.
The document discusses various computational models for semiconductor device transport simulation. It begins by describing semiclassical transport theory and approaches like drift-diffusion, hydrodynamics, and particle-based Monte Carlo methods. It then covers topics like inclusion of tunneling effects, quantum corrections, and particle-based and quantum transport simulations. Specific models are discussed for generation-recombination mechanisms, low-field and field-dependent mobility, inversion layer mobility, and the hydrodynamic approach for including velocity overshoot effects.
Ch4 lecture slides Chenming Hu Device for ICChenming Hu
The document discusses PN junctions and their properties. It covers:
1) The basic structure of a PN junction and its energy band diagram under equilibrium conditions. A depletion region forms where the bands bend.
2) The built-in potential that exists across the depletion region due to the diffusion of charge carriers. This potential can be calculated from the doping concentrations.
3) The behavior of a PN junction under forward and reverse bias, including how the depletion region width changes with applied voltage. Carrier injection also occurs under forward bias.
4) Breakdown mechanisms that can occur under high reverse bias, including avalanche and tunneling breakdown. Zener diodes are designed to operate
James Clerk Maxwell's equations represent the fundamentals of electricity and magnetism in an elegant and concise form. The document discusses various units used to measure magnetic flux, such as the Maxwell and Weber. It then examines Maxwell's modifications to Ampere's law by including the concept of displacement current to account for changing electric fields producing magnetic fields. As an example, the document calculates the magnetic field produced near a parallel plate capacitor due to the changing electric field between its plates.
The document summarizes research on understanding charge transport in low dimensional semiconductor nanostructures embedded in an insulating matrix. Specifically, it examines current-voltage characteristics of germanium nanowire arrays in an alumina matrix as a function of temperature. Key findings include:
1) At room temperature, conduction follows Ohm's law at low voltages and Mott-Gurney's space charge limited current law at higher voltages.
2) With decreasing temperature, conduction transitions from a trap-free regime to an exponentially distributed trap regime.
3) Mobility decreases with decreasing temperature, and activation energy is extracted from an Arrhenius plot, found to be 85 meV at low temperatures and 301 meV
International Journal of Engineering Research and Development (IJERD)IJERD Editor
journal publishing, how to publish research paper, Call For research paper, international journal, publishing a paper, IJERD, journal of science and technology, how to get a research paper published, publishing a paper, publishing of journal, publishing of research paper, reserach and review articles, IJERD Journal, How to publish your research paper, publish research paper, open access engineering journal, Engineering journal, Mathemetics journal, Physics journal, Chemistry journal, Computer Engineering, Computer Science journal, how to submit your paper, peer reviw journal, indexed journal, reserach and review articles, engineering journal, www.ijerd.com, research journals,
yahoo journals, bing journals, International Journal of Engineering Research and Development, google journals, hard copy of journal
chapter 21Electric charge and electric field.pdfssusercceaa8
The document discusses electric charge and the electric field. It defines electric charge as a fundamental property of matter that can be positive or negative. Benjamin Franklin established that positive charge is possessed by protons and negative charge by electrons. Charges of the same sign repel, while opposite charges attract. Coulomb's law states that the electrostatic force between two point charges is directly proportional to the product of their charges and inversely proportional to the square of the distance between them. The electric field is defined as the electric force on a small test charge divided by that test charge. It is represented by field lines that indicate the direction and strength of the field.
Kinetics of X-ray conductivity for an ideal wide-gap semiconductor irradiated...Andrii Sofiienko
This document discusses the development of a kinetic theory to describe the X-ray conductivity (XRC) of semiconductors and dielectrics when irradiated by X-rays. It begins by outlining the need for such a theory and which characteristics it should describe. It then presents the initial stages of developing the theory, including modeling an ideal semiconductor at low excitation levels and deriving expressions for the spatial distribution of free electrons and holes and their lifetimes. The document also examines how the electric field of free charge carriers affects the distributions as excitation increases and considers incorporating the Coulomb interaction between carriers.
"IOS 18 CONTROL CENTRE REVAMP STREAMLINED IPHONE SHUTDOWN MADE EASIER"Emmanuel Onwumere
In iOS 18, Apple has introduced a significant revamp to the Control Centre, making it more intuitive and user-friendly. One of the standout features is a quicker and more accessible way to shut down your iPhone. This enhancement aims to streamline the user experience, allowing for faster access to essential functions. Discover how iOS 18's redesigned Control Centre can simplify your daily interactions with your iPhone, bringing convenience right at your fingertips.
Building a Raspberry Pi Robot with Dot NET 8, Blazor and SignalRPeter Gallagher
In this session delivered at NDC Oslo 2024, I talk about how you can control a 3D printed Robot Arm with a Raspberry Pi, .NET 8, Blazor and SignalR.
I also show how you can use a Unity app on an Meta Quest 3 to control the arm VR too.
You can find the GitHub repo and workshop instructions here;
https://bit.ly/dotnetrobotgithub
1. Modern Semiconductor Devices for Integrated Circuits (C. Hu) Slide 2-1
Chapter 2 Motion and Recombination
of Electrons and Holes
2.1 Thermal Motion
Average electron or hole kinetic energy 2
2
1
2
3
th
mv
kT
kg
10
1
.
9
26
.
0
K
300
JK
10
38
.
1
3
3
31
1
23
eff
th
m
kT
v
cm/s
10
3
.
2
m/s
10
3
.
2 7
5
2. Modern Semiconductor Devices for Integrated Circuits (C. Hu) Slide 2-2
2.1 Thermal Motion
• Zig-zag motion is due to collisions or scattering
with imperfections in the crystal.
• Net thermal velocity is zero.
• Mean time between collisions is m ~ 0.1ps
3. Modern Semiconductor Devices for Integrated Circuits (C. Hu) Slide 2-3
Hot-point Probe can determine sample doing type
Thermoelectric Generator
(from heat to electricity )
and Cooler (from
electricity to refrigeration)
Hot-point Probe
distinguishes N
and P type
semiconductors.
4. Modern Semiconductor Devices for Integrated Circuits (C. Hu) Slide 2-4
2.2 Drift
2.2.1 Electron and Hole Mobilities
• Drift is the motion caused by an electric field.
5. Modern Semiconductor Devices for Integrated Circuits (C. Hu) Slide 2-5
2.2.1 Electron and Hole Mobilities
• p is the hole mobility and n is the electron mobility
mp
p
q
v
m
E
p
mp
m
q
v
E
p
mp
p
m
q
n
mn
n
m
q
E
p
v
E
n
v
6. Modern Semiconductor Devices for Integrated Circuits (C. Hu) Slide 2-6
Electron and hole mobilities of selected
semiconductors
2.2.1 Electron and Hole Mobilities
Si Ge GaAs InAs
n (cm2
/V∙s) 1400 3900 8500 30000
p (cm2
/V∙s) 470 1900 400 500
.
s
V
cm
V/cm
cm/s 2
v = E ; has the dimensions of v/E
Based on the above table alone, which semiconductor and which carriers
(electrons or holes) are attractive for applications in high-speed devices?
7. Modern Semiconductor Devices for Integrated Circuits (C. Hu) Slide 2-7
EXAMPLE: Given p = 470 cm2/V·s, what is the hole drift velocity at
E = 103 V/cm? What is mp and what is the distance traveled between
collisions (called the mean free path)? Hint: When in doubt, use the
MKS system of units.
Solution: n = pE = 470 cm2/V·s 103 V/cm = 4.7 105 cm/s
mp = pmp/q =470 cm2/V ·s 0.39 9.110-31 kg/1.610-19 C
= 0.047 m2/V ·s 2.210-12 kg/C = 110-13s = 0.1 ps
mean free path = mhnth ~ 1 10-13 s 2.2107 cm/s
= 2.210-6 cm = 220 Å = 22 nm
This is smaller than the typical dimensions of devices, but getting close.
Drift Velocity, Mean Free Time, Mean Free Path
8. Modern Semiconductor Devices for Integrated Circuits (C. Hu) Slide 2-8
There are two main causes of carrier scattering:
1. Phonon Scattering
2. Ionized-Impurity (Coulombic) Scattering
2
/
3
2
/
1
1
1
T
T
T
velocity
thermal
carrier
density
phonon
phonon
phonon
Phonon scattering mobility decreases when temperature rises:
= q/m
vth T1/2
2.2.2 Mechanisms of Carrier Scattering
T
9. Modern Semiconductor Devices for Integrated Circuits (C. Hu) Slide 2-9
_
+
- -
Electron
Boron Ion Electron
Arsenic
Ion
Impurity (Dopant)-Ion Scattering or Coulombic Scattering
d
a
d
a
th
impurity
N
N
T
N
N
v
2
/
3
3
There is less change in the direction of travel if the electron zips by
the ion at a higher speed.
10. Modern Semiconductor Devices for Integrated Circuits (C. Hu)
Slide 2-10
Total Mobility
1E14 1E15 1E16 1E17 1E18 1E19 1E20
0
200
400
600
800
1000
1200
1400
1600
Holes
Electrons
Mobility
(cm
2
V
-1
s
-1
)
Total Impurity Concenration (atoms cm
-3
)
Na + Nd (cm-3)
impurity
phonon
impurity
phonon
1
1
1
1
1
1
11. Modern Semiconductor Devices for Integrated Circuits (C. Hu) Slide 2-11
Temperature Effect on Mobility
1015
Question:
What Nd will make
dn/dT = 0 at room
temperature?
12. Modern Semiconductor Devices for Integrated Circuits (C. Hu) Slide 2-12
Velocity Saturation
• When the kinetic energy of a carrier exceeds a critical value, it
generates an optical phonon and loses the kinetic energy.
• Therefore, the kinetic energy is capped at large E, and the
velocity does not rise above a saturation velocity, vsat .
• Velocity saturation has a deleterious effect on device speed as
shown in Ch. 6.
13. Modern Semiconductor Devices for Integrated Circuits (C. Hu) Slide 2-13
2.2.3 Drift Current and Conductivity
Jp
n
E
unit
area
+
+
Jp = qpv A/cm2 or C/cm2·sec
If p = 1015cm-3 and v = 104 cm/s, then
Jp= 1.610-19C 1015cm-3 104cm/s
= 2
2
A/cm
1.6
cm
C/s
6
.
1
EXAMPLE:
Hole current density
14. Modern Semiconductor Devices for Integrated Circuits (C. Hu) Slide 2-14
Jp,drift = qpv = qppE
Jn,drift = –qnv = qnnE
Jdrift = Jn,drift + Jp,drift = E =(qnn+qpp)E
conductivity (1/ohm-cm) of a semiconductor is
= qnn + qpp
2.2.3 Drift Current and Conductivity
1/ = is resistivity (ohm-cm)
15. Modern Semiconductor Devices for Integrated Circuits (C. Hu) Slide 2-15
N-type
P-type
Relationship between Resistivity and Dopant Density
= 1/
DOPANT
DENSITY
cm
-3
RESISTIVITY (cm)
16. Modern Semiconductor Devices for Integrated Circuits (C. Hu) Slide 2-16
EXAMPLE: Temperature Dependence of Resistance
(a) What is the resistivity () of silicon doped
with 1017cm-3 of arsenic?
Solution:
(a) Using the N-type curve in the previous
figure, we find that = 0.084 -cm.
(b) What is the resistance (R) of a piece of this
silicon material 1m long and 0.1 m2 in cross-
sectional area?
(b) R = L/A = 0.084 -cm 1 m / 0.1 m2
= 0.084 -cm 10-4 cm/ 10-10 cm2
= 8.4 10-4
17. Modern Semiconductor Devices for Integrated Circuits (C. Hu) Slide 2-17
EXAMPLE: Temperature Dependence of Resistance
By what factor will R increase or decrease from
T=300 K to T=400 K?
Solution: The temperature dependent factor in (and
therefore ) is n. From the mobility vs. temperature
curve for 1017cm-3, we find that n decreases from 770
at 300K to 400 at 400K. As a result, R increases by
93
.
1
400
770
18. Modern Semiconductor Devices for Integrated Circuits (C. Hu) Slide 2-18
2.3 Diffusion Current
Particles diffuse from a higher-concentration location
to a lower-concentration location.
19. Modern Semiconductor Devices for Integrated Circuits (C. Hu) Slide 2-19
2.3 Diffusion Current
dx
dn
qD
J n
diffusion
n
,
dx
dp
qD
J p
diffusion
p
,
D is called the diffusion constant. Signs explained:
n p
x x
20. Modern Semiconductor Devices for Integrated Circuits (C. Hu) Slide 2-20
Total Current – Review of Four Current Components
Jn = Jn,drift + Jn,diffusion = qnnE +
dx
dn
qDn
Jp = Jp,drift + Jp,diffusion = qppE –
dx
dp
qDp
JTOTAL = Jn + Jp
21. Modern Semiconductor Devices for Integrated Circuits (C. Hu) Slide 2-21
2.4 Relation Between the Energy
Diagram and V, E
E(x)=
dx
dE
q
1
dx
dE
q
1
dx
dV v
c
Ec and Ev vary in the opposite
direction from the voltage. That
is, Ec and Ev are higher where
the voltage is lower.
+ –
Si
E
x
Ec(x)
Ef(x)
Ev(x)
E
0.7V
-
+
V(x)
0.7V
x
0
(a)
(b)
(c)
x
Ef (x)
E
0.7V
-
+
Ec(x)
Ev(x)
N-
+ –
0.7eV
N type Si
22. Modern Semiconductor Devices for Integrated Circuits (C. Hu) Slide 2-22
2.5 Einstein Relationship between D and
dx
dE
e
kT
N
dx
dn c
kT
/
)
E
E
(
c f
c
dx
dE
kT
n c
kT
/
)
E
E
(
c
f
c
e
N
n
Consider a piece of non-uniformly doped semiconductor.
Ev(x)
Ec(x)
Ef
n-type semiconductor
Decreasing donor concentration
Ec(x)
Ef
N-type semiconductor
E
q
kT
n
23. Modern Semiconductor Devices for Integrated Circuits (C. Hu) Slide 2-23
2.5 Einstein Relationship between D and
E
q
kT
n
dx
dn
0
dx
dn
qD
qn
J n
n
n E
at equilibrium.
E
E
kT
qD
qn
qn n
n
0
n
n
q
kT
D
These are known as the Einstein relationship.
p
p
q
kT
D
Similarly,
24. Modern Semiconductor Devices for Integrated Circuits (C. Hu) Slide 2-24
EXAMPLE: Diffusion Constant
What is the hole diffusion constant in a piece of
silicon with p = 410 cm2 V-1s-1 ?
Solution:
Remember: kT/q = 26 mV at room temperature.
/s
cm
1
1
s
V
cm
410
)
mV
26
( 2
1
1
2
p
p
q
kT
D
25. Modern Semiconductor Devices for Integrated Circuits (C. Hu) Slide 2-25
2.6 Electron-Hole Recombination
•The equilibrium carrier concentrations are denoted with
n0 and p0.
•The total electron and hole concentrations can be different
from n0 and p0 .
•The differences are called the excess carrier
concentrations n’ and p’.
'
0 n
n
n
'
0 p
p
p
26. Modern Semiconductor Devices for Integrated Circuits (C. Hu) Slide 2-26
Charge Neutrality
•Charge neutrality is satisfied at equilibrium (n’=
p’= 0).
• When a non-zero n’is present, an equal p’may
be assumed to be present to maintain charge
equality and vice-versa.
•If charge neutrality is not satisfied, the net charge
will attract or repel the (majority) carriers through
the drift current until neutrality is restored.
'
p
'
n
27. Modern Semiconductor Devices for Integrated Circuits (C. Hu) Slide 2-27
Recombination Lifetime
•Assume light generates n’and p’. If the light is
suddenly turned off, n’and p’decay with time
until they become zero.
•The process of decay is called recombination.
•The time constant of decay is the recombination
time or carrier lifetime, .
•Recombination is nature’s way of restoring
equilibrium (n’= p’= 0).
28. Modern Semiconductor Devices for Integrated Circuits (C. Hu) Slide 2-28
• ranges from 1ns to 1ms in Si and depends on
the density of metal impurities (contaminants)
such as Au and Pt.
•These deep traps capture electrons and holes to
facilitate recombination and are called
recombination centers.
Recombination Lifetime
Ec
Ev
Direct
Recombination
is unfavorable in
silicon
Recombination
centers
29. Direct and Indirect Band Gap
Direct band gap
Example: GaAs
Direct recombination is efficient
as k conservation is satisfied.
Indirect band gap
Example: Si
Direct recombination is rare as k
conservation is not satisfied
Trap
Modern Semiconductor Devices for Integrated Circuits (C. Hu)
30. Modern Semiconductor Devices for Integrated Circuits (C. Hu) Slide 2-30
n
dt
n
d
dt
p
d
p
n
dt
n
d
Rate of recombination (s-1cm-3)
p
n
31. Modern Semiconductor Devices for Integrated Circuits (C. Hu) Slide 2-31
EXAMPLE: Photoconductors
A bar of Si is doped with boron at 1015cm-3. It is
exposed to light such that electron-hole pairs are
generated throughout the volume of the bar at the
rate of 1020/s·cm3. The recombination lifetime is
10s. What are (a) p0 , (b) n0 , (c) p’, (d) n’, (e) p ,
(f) n, and (g) the np product?
32. Modern Semiconductor Devices for Integrated Circuits (C. Hu) Slide 2-32
EXAMPLE: Photoconductors
Solution:
(a) What is p0?
p0 = Na = 1015 cm-3
(b) What is n0 ?
n0 = ni
2/p0 = 105 cm-3
(c) What is p’?
In steady-state, the rate of generation is equal to the
rate of recombination.
1020/s-cm3 = p’/
p’= 1020/s-cm3 · 10-5s = 1015 cm-3
33. Modern Semiconductor Devices for Integrated Circuits (C. Hu) Slide 2-33
EXAMPLE: Photoconductors
(d) What is n’?
n’= p’= 1015 cm-3
(e) What is p?
p = p0 + p’= 1015cm-3 + 1015cm-3 = 2×1015cm-3
(f) What is n?
n = n0 + n’= 105cm-3 + 1015cm-3 ~ 1015cm-3 since n0 << n’
(g) What is np?
np ~ 21015cm-3 ·1015cm-3 = 21030 cm-6 >> ni
2 = 1020 cm-6.
The np product can be very different from ni
2.
34. Modern Semiconductor Devices for Integrated Circuits (C. Hu) Slide 2-34
2.7 Thermal Generation
If n’is negative, there are fewer
electrons than the equilibrium value.
As a result, there is a net rate of
thermal generation at the rate of |n|/ .
35. Modern Semiconductor Devices for Integrated Circuits (C. Hu) Slide 2-35
2.8 Quasi-equilibrium and Quasi-Fermi Levels
• Whenever n’= p’ 0, np ni
2. We would like to preserve
and use the simple relations:
• But these equations lead to np = ni
2. The solution is to introduce
two quasi-Fermi levels Efn and Efp such that
kT
E
E
c
f
c
e
N
n
/
)
(
kT
E
E
v
v
f
e
N
p
/
)
(
kT
E
E
c
fn
c
e
N
n
/
)
(
kT
E
E
v
v
fp
e
N
p
/
)
(
Even when electrons and holes are not at equilibrium, within
each group the carriers can be at equilibrium. Electrons are
closely linked to other electrons but only loosely to holes.
36. Modern Semiconductor Devices for Integrated Circuits (C. Hu) Slide 2-36
EXAMPLE: Quasi-Fermi Levels and Low-Level Injection
Consider a Si sample with Nd=1017cm-3 and n’=p’=1015cm-3.
(a) Find Ef .
n = Nd = 1017 cm-3 = Ncexp[–(Ec– Ef)/kT]
Ec– Ef = 0.15 eV. (Ef is below Ec by 0.15 eV.)
Note: n’and p’are much less than the majority carrier
concentration. This condition is called low-level
injection.
37. Modern Semiconductor Devices for Integrated Circuits (C. Hu) Slide 2-37
Now assume n = p = 1015 cm-3.
(b) Find Efn and Efp .
n = 1.011017cm-3 =
Ec–Efn = kT ln(Nc/1.011017cm-3)
= 26 meV ln(2.81019cm-3/1.011017cm-3)
= 0.15 eV
Efn is nearly identical to Ef because n n0 .
kT
E
E
c
fn
c
e
N
/
)
(
EXAMPLE: Quasi-Fermi Levels and Low-Level Injection
38. Modern Semiconductor Devices for Integrated Circuits (C. Hu) Slide 2-38
EXAMPLE: Quasi-Fermi Levels
p = 1015 cm-3 =
Efp–Ev = kT ln(Nv/1015cm-3)
= 26 meV ln(1.041019cm-3/1015cm-3)
= 0.24 eV
kT
E
E
v
v
fp
e
N
/
)
(
Ec
Ev
Efp
Ef Efn
39. Modern Semiconductor Devices for Integrated Circuits (C. Hu) Slide 2-39
2.9 Chapter Summary
dx
dn
qD
J n
diffusion
n
,
dx
dp
qD
J p
diffusion
p
,
n
n
q
kT
D
p
p
q
kT
D
E
p
p
v
E
n
n
v
E
p
drift
p qp
J
,
E
n
drift
n qn
J
,
-
40. Modern Semiconductor Devices for Integrated Circuits (C. Hu) Slide 2-40
2.9 Chapter Summary
is the recombination lifetime.
n’and p’are the excess carrier concentrations.
n = n0+ n’
p = p0+ p’
Charge neutrality requires n’= p’.
rate of recombination = n’/ = p’/
Efn and Efp are the quasi-Fermi levels of electrons and
holes.
kT
E
E
v
v
fp
e
N
p
/
)
(
kT
E
E
c
fn
c
e
N
n
/
)
(