EE495/695 Introduction to Semiconductors I. Y. Baghzouz ECE Department UNLV

Size: px
Start display at page:

Download "EE495/695 Introduction to Semiconductors I. Y. Baghzouz ECE Department UNLV"

Transcription

1 EE495/695 Introduction to Semiconductors I Y. Baghzouz ECE Department UNLV

2 Introduction Solar cells have always been aligned closely with other electronic devices. We will cover the basic aspects of semiconductor materials and the physical mechanisms which are at the centre of photovoltaic devices. These physical mechanisms are used to explain the operation of a p-n junction, which forms the basis of the greatest majority of solar cells An ingot of silicon, consisting of a single large crystal of silicon.

3 Semiconductor Structure Semiconductors are made up of individual atoms bonded together in a regular, periodic structure to form an arrangement whereby each atom is surrounded by 8 electrons. An individual atom consists of a nucleus made up of a core of protons (positively charged particles) and neutrons (particles having no charge) surrounded by electrons. The number of electrons and protons is equal, such that the atom is overall electrically neutral. The electrons occupy certain energy levels, based on the number of electrons in the atom, which is different for each element in the periodic table. structure of a semiconductor

4 Semiconductors The atoms in a semiconductor are materials from either group IV of the periodic table, or from a combination of group III & V (III-V semiconductors), or II & VI (II- VI semiconductors). Silicon (Si) is the most commonly used semiconductor material as it forms the basis for integrated circuit (IC) chips and is the most mature technology. Most solar cells are also silicon-based. Other common semiconductors include Ge, GaAs, and CdTe. Section from the periodic table - Most common semiconductor materials shown in blue.

5 Silicon (Si) Atom Most solar cells are made from silicon (14 th element). Silicon is a "semi-conductor" or a "semi-metal," and has properties of both a metal and an insulator. Silicon has 14 electrons. The outermost four electrons, called valence electrons, play a very important role in the photoelectric effect. In a crystalline solid, a silicon atom shares each of its four valence electrons with each of four neighboring atoms.

6 Bond Structure of Si The bond structure of a semiconductor determines the material properties of a semiconductor. The electrons surrounding each atom in a semiconductor are part of a covalent bond, (i.e., two atoms "sharing" a single electron). The electrons in the covalent bond are held in place by this bond and hence they are localized to the region surrounding the atom. However, only at absolute zero temperature are all electrons in a bonded arrangement (insulator). At elevated temperatures, these electrons can gain enough energy to escape from their bond (conductor). At room temperature, a semiconductor has enough free electrons to allow it to conduct limited current (semiconductor).

7 Band Gap The presence of the bond introduces two distinct energy states for the electrons. The lowest energy position - bound state. If the electron has enough thermal energy to break free of its bond, then it is in a - free state. The electron cannot attain energy values intermediate to these two levels; it is either at a low energy position, or it has gained enough energy to break free and therefore has a certain minimum energy. This minimum energy is called the "band gap" of a semiconductor. The space left behind by the electrons allows a covalent bond to move from one electron to another, thus appearing to be a positive charge moving through the crystal lattice. This empty space is commonly called a "hole", and is similar to an electron, but with a positive charge. Formation of "free" electrons and holes when an electron can escape its bond.

8 Band Diagram Most important parameters of semiconductor material for solar cell operation: the band gap; the number of free carriers (free electrons and resulting holes) available for conduction; the "generation" and recombination of free carriers in response to light shining on the material. The band gap of a semiconductor is the minimum energy required to move an electron from its bound state to a free state where it can participate in conduction. The band structure of a semiconductor that gives the energy of the electrons on the y-axis and is called a "band diagram". The lower energy level of a semiconductor is called the "valence band" and the energy level at which an electron can be considered free is called the "conduction band". The band gap is the distance between the conduction band and valence band.

9 Intrinsic Carrier Concentration The thermal excitation of electrons from the valence band to the conduction band creates free carriers in both bands. The concentration of these carriers in intrinsic materials (semiconductor with no added impurities) is called the intrinsic carrier concentration, n i. n i is the number of electrons in the conduction band or the number of holes in the valence band in intrinsic material. n i depends on the band gap and on the temperature of the material. A large band gap will make it more difficult for a carrier to be thermally excited, hence n i is lower in higher band gap materials. Alternatively, increasing the temperature makes it more likely that an electron will be excited into the conduction band, which will increase n i. T0 T1> T0 T2> T1

10 Intrinsic Carrier Concentration At 300 K the generally accepted value for the intrinsic carrier concentration of silicon, n i = 1.01 x /cm 3 [1]. An empirical fit to the measured data over the range 275 K to 375 K is given by: where T is in deg. K. Question: find the intrinsic carrier concentration of Si at 25 C and at 95 F. [K] = ([ F] ) 5 9 [K] = [ C] [1] Sproul A.B., Green M.A., "Improved Value for the Silicon Intrinsic Carrier Concentration from 275 to 300K", J. Appl. Physics., 70,

11 Doping It is possible to shift the balance of electrons and holes in a silicon crystal lattice by "doping" it with impurities. Atoms with one more valence electron than silicon (e.g., phosphorous) are used to produce "n-type" material, which adds electrons to the conduction band. Atoms with one less valence electron (e.g. boron) result in "p-type" material where the number of electrons trapped in bonds is higher, thus increasing the number of holes. In doped materials, there is always more of one type of carrier than the other.

12 Doping The type of carrier with the higher concentration is called a "majority carrier", while the lower concentration carrier is called a "minority carrier." In a typical doped semiconductor, there might be /cm 3 majority carriers and 10 6 /cm 3 minority carriers. The ratio of minority to majority carriers is less than one person to the entire population of the planet. Minority carriers are created either thermally or by incident photons. N P

13 Equilibrium Carrier Concentration The number of carriers in the conduction and valence band with no externally applied energy source is called the equilibrium carrier concentration. For majority carriers, the equilibrium carrier concentration is equal to the intrinsic carrier concentration plus the number of free carriers added by doping the semiconductor. Under most conditions, the doping of the semiconductor is several orders of magnitude greater than the intrinsic carrier concentration, such that the number of majority carriers is approximately equal to that due to doping.

14 Equilibrium Carrier Concentration At equilibrium, the product of the majority and minority carrier concentration is constant, and this is mathematically expressed by the Law of Mass Action: where n i is the intrinsic carrier concentration and n 0 and p 0 are the electron and hole equilibrium carrier concentrations. Intrinsic material Material doped moderately with group V Material heavily doped with group V

15 Absorption of Light Photons incident on the surface of a semiconductor will be either reflected from the top surface, absorbed in the material, or transmitted through the material. For photovoltaic devices, reflection and transmission are typically considered loss mechanisms as photons which are not absorbed do not generate power. If the photon is absorbed, it will raise an electron from the valence band to the conduction band. A key factor in determining if a photon is absorbed is the energy of the photon. Photons falling onto a semiconductor material can be divided into three groups based on their energy compared to that of the semiconductor band gap:

16 Absorption of Light E ph < E G : Photons with energy E ph less than the band gap energy E G interact only weakly with the semiconductor, passing through it as if it were transparent. E ph = E G : Photons have just enough energy to create an electron hole pair and are efficiently absorbed. E ph > E G : Photons with energy greater than the band gap are strongly absorbed. The number of light-generated majority carriers are often orders of magnitude less than the number of majority carriers already present in the solar cell due to doping. Hence, the number of majority carriers in an illuminated semiconductor does not alter significantly. The number of photo-generated minority carriers outweighs the number of minority carriers existing in the solar cell in the dark. Therefore, the number of minority carriers in an illuminated solar cell can be approximated by the number of light generated carriers.

17 Absorption Depth Different wavelengths penetrate different distances into a semiconductor before most of the light is absorbed. The absorption depth is a useful parameter which gives the distance into the material at which the light drops to about 36% (or 1/e) of its original intensity. High energy light (blue) is absorbed within a few microns, while low energy (red) is absorbed after a few hundred microns. The blue photons are absorbed very close to the surface but most of the red photons are absorbed deep in the device

18 Absorption depth of common semiconductor materials 300 o K)

19 Generation Rate The generation rate gives the number of electrons generated at each point in the device due to the absorption of photons. Neglecting reflection, the amount of light which is absorbed by a material depends on the absorption coefficient (in cm -1 ) and the thickness of the material. The intensity of light at any point in the device can be calculated according to the equation below: where α is the absorption coefficient (in cm -1 ), x is the distance (in cm) into the material at which the light intensity is being calculated; and I 0 is the light intensity at the top surface.

20 Generation Rate Assuming that the loss in light intensity (i.e., the absorption of photons) directly causes the generation of an electron-hole pair, then the generation G in a thin slice of material is determined by finding the change in light intensity across this slice. Consequently, differentiating the previous equation will give the generation rate at any point in the device: G x = αi e α 0 where I 0 = photon flux at the surface (photons/unit-area/sec.); α = absorption coefficient; and x = distance into the material. For photovoltaic applications, the incident light consists of a combination of many different wavelengths, and therefore the generation rate at each wavelength is different. The net generation is the sum of the generation for each wavelength.

21 Generation Rate The generation as a function of cell depth for a standard solar spectrum (AM 1.5) incident on a piece of silicon is shown below. Note: there is an enormously greater generation of electron-hole pairs near the front surface of the cell, while further into the solar cell the generation rate becomes nearly constant.

22 Recombination Any electron which exists in the conduction band is in a meta-stable state and will eventually fall back to a lower energy position in the valance band. When the electron falls back down into the valence band, it removes a hole. This process is called recombination.

23 Surface Recombination Any defects or impurities at the surface of the semiconductor promote recombination. Since the surface of the solar cell represents a severe disruption of the crystal lattice, the surfaces of the solar cell are a site of particularly high recombination. The high recombination rate in the vicinity of a surface depletes this region of minority carriers. A localized region of low carrier concentration causes carriers to flow into this region from the surroundings with higher concentration regions. Therefore, the surface recombination rate is limited by the rate at which minority carriers move towards the surface.

24 Surface Recombination The defects at a semiconductor surface are caused by the interruption to the periodicity of the crystal lattice, which causes dangling bonds at the semiconductor surface. The reduction of the number of dangling bonds, and hence the recombination, is achieved by growing a layer on top of the semiconductor surface which ties up some of these dangling bonds. This reduction of dangling bonds in known as surface passivation.

3.1 Introduction to Semiconductors. Y. Baghzouz ECE Department UNLV

3.1 Introduction to Semiconductors. Y. Baghzouz ECE Department UNLV 3.1 Introduction to Semiconductors Y. Baghzouz ECE Department UNLV Introduction In this lecture, we will cover the basic aspects of semiconductor materials, and the physical mechanisms which are at the

More information

EE 446/646 Photovoltaic Devices I. Y. Baghzouz

EE 446/646 Photovoltaic Devices I. Y. Baghzouz EE 446/646 Photovoltaic Devices I Y. Baghzouz What is Photovoltaics? First used in about 1890, the word has two parts: photo, derived from the Greek word for light, volt, relating to electricity pioneer

More information

Electrons are shared in covalent bonds between atoms of Si. A bound electron has the lowest energy state.

Electrons are shared in covalent bonds between atoms of Si. A bound electron has the lowest energy state. Photovoltaics Basic Steps the generation of light-generated carriers; the collection of the light-generated carriers to generate a current; the generation of a large voltage across the solar cell; and

More information

Atoms? All matters on earth made of atoms (made up of elements or combination of elements).

Atoms? All matters on earth made of atoms (made up of elements or combination of elements). Chapter 1 Atoms? All matters on earth made of atoms (made up of elements or combination of elements). Atomic Structure Atom is the smallest particle of an element that can exist in a stable or independent

More information

The photovoltaic effect occurs in semiconductors where there are distinct valence and

The photovoltaic effect occurs in semiconductors where there are distinct valence and How a Photovoltaic Cell Works The photovoltaic effect occurs in semiconductors where there are distinct valence and conduction bands. (There are energies at which electrons can not exist within the solid)

More information

Basic Semiconductor Physics

Basic Semiconductor Physics 6 Basic Semiconductor Physics 6.1 Introduction With this chapter we start with the discussion of some important concepts from semiconductor physics, which are required to understand the operation of solar

More information

Lecture 1. OUTLINE Basic Semiconductor Physics. Reading: Chapter 2.1. Semiconductors Intrinsic (undoped) silicon Doping Carrier concentrations

Lecture 1. OUTLINE Basic Semiconductor Physics. Reading: Chapter 2.1. Semiconductors Intrinsic (undoped) silicon Doping Carrier concentrations Lecture 1 OUTLINE Basic Semiconductor Physics Semiconductors Intrinsic (undoped) silicon Doping Carrier concentrations Reading: Chapter 2.1 EE105 Fall 2007 Lecture 1, Slide 1 What is a Semiconductor? Low

More information

PHOTOVOLTAICS Fundamentals

PHOTOVOLTAICS Fundamentals PHOTOVOLTAICS Fundamentals PV FUNDAMENTALS Semiconductor basics pn junction Solar cell operation Design of silicon solar cell SEMICONDUCTOR BASICS Allowed energy bands Valence and conduction band Fermi

More information

electronics fundamentals

electronics fundamentals electronics fundamentals circuits, devices, and applications THOMAS L. FLOYD DAVID M. BUCHLA Lesson 1: Diodes and Applications Semiconductors Figure 1-1 The Bohr model of an atom showing electrons in orbits

More information

SEMICONDUCTOR PHYSICS REVIEW BONDS,

SEMICONDUCTOR PHYSICS REVIEW BONDS, SEMICONDUCTOR PHYSICS REVIEW BONDS, BANDS, EFFECTIVE MASS, DRIFT, DIFFUSION, GENERATION, RECOMBINATION February 3, 2011 The University of Toledo, Department of Physics and Astronomy SSARE, PVIC Principles

More information

3.1 Absorption and Transparency

3.1 Absorption and Transparency 3.1 Absorption and Transparency 3.1.1 Optical Devices (definitions) 3.1.2 Photon and Semiconductor Interactions 3.1.3 Photon Intensity 3.1.4 Absorption 3.1 Absorption and Transparency Objective 1: Recall

More information

ET3034TUx Utilization of band gap energy

ET3034TUx Utilization of band gap energy ET3034TUx - 3.3.1 - Utilization of band gap energy In the last two weeks we have discussed the working principle of a solar cell and the external parameters that define the performance of a solar cell.

More information

EE143 Fall 2016 Microfabrication Technologies. Evolution of Devices

EE143 Fall 2016 Microfabrication Technologies. Evolution of Devices EE143 Fall 2016 Microfabrication Technologies Prof. Ming C. Wu wu@eecs.berkeley.edu 511 Sutardja Dai Hall (SDH) 1-1 Evolution of Devices Yesterday s Transistor (1947) Today s Transistor (2006) 1-2 1 Why

More information

EECS143 Microfabrication Technology

EECS143 Microfabrication Technology EECS143 Microfabrication Technology Professor Ali Javey Introduction to Materials Lecture 1 Evolution of Devices Yesterday s Transistor (1947) Today s Transistor (2006) Why Semiconductors? Conductors e.g

More information

Engineering 2000 Chapter 8 Semiconductors. ENG2000: R.I. Hornsey Semi: 1

Engineering 2000 Chapter 8 Semiconductors. ENG2000: R.I. Hornsey Semi: 1 Engineering 2000 Chapter 8 Semiconductors ENG2000: R.I. Hornsey Semi: 1 Overview We need to know the electrical properties of Si To do this, we must also draw on some of the physical properties and we

More information

Chemistry Instrumental Analysis Lecture 8. Chem 4631

Chemistry Instrumental Analysis Lecture 8. Chem 4631 Chemistry 4631 Instrumental Analysis Lecture 8 UV to IR Components of Optical Basic components of spectroscopic instruments: stable source of radiant energy transparent container to hold sample device

More information

EECS130 Integrated Circuit Devices

EECS130 Integrated Circuit Devices EECS130 Integrated Circuit Devices Professor Ali Javey 8/30/2007 Semiconductor Fundamentals Lecture 2 Read: Chapters 1 and 2 Last Lecture: Energy Band Diagram Conduction band E c E g Band gap E v Valence

More information

Electro - Principles I

Electro - Principles I Electro - Principles I Page 10-1 Atomic Theory It is necessary to know what goes on at the atomic level of a semiconductor so the characteristics of the semiconductor can be understood. In many cases a

More information

ECE 250 Electronic Devices 1. Electronic Device Modeling

ECE 250 Electronic Devices 1. Electronic Device Modeling ECE 250 Electronic Devices 1 ECE 250 Electronic Device Modeling ECE 250 Electronic Devices 2 Introduction to Semiconductor Physics You should really take a semiconductor device physics course. We can only

More information

February 1, 2011 The University of Toledo, Department of Physics and Astronomy SSARE, PVIC

February 1, 2011 The University of Toledo, Department of Physics and Astronomy SSARE, PVIC FUNDAMENTAL PROPERTIES OF SOLAR CELLS February 1, 2011 The University of Toledo, Department of Physics and Astronomy SSARE, PVIC Principles and Varieties of Solar Energy (PHYS 4400) and Fundamentals of

More information

CLASS 1 & 2 REVISION ON SEMICONDUCTOR PHYSICS. Reference: Electronic Devices by Floyd

CLASS 1 & 2 REVISION ON SEMICONDUCTOR PHYSICS. Reference: Electronic Devices by Floyd CLASS 1 & 2 REVISION ON SEMICONDUCTOR PHYSICS Reference: Electronic Devices by Floyd 1 ELECTRONIC DEVICES Diodes, transistors and integrated circuits (IC) are typical devices in electronic circuits. All

More information

Semiconductors 1. Explain different types of semiconductors in detail with necessary bond diagrams. Intrinsic semiconductors:

Semiconductors 1. Explain different types of semiconductors in detail with necessary bond diagrams. Intrinsic semiconductors: Semiconductors 1. Explain different types of semiconductors in detail with necessary bond diagrams. There are two types of semi conductors. 1. Intrinsic semiconductors 2. Extrinsic semiconductors Intrinsic

More information

Lecture 2 Electrons and Holes in Semiconductors

Lecture 2 Electrons and Holes in Semiconductors EE 471: Transport Phenomena in Solid State Devices Spring 2018 Lecture 2 Electrons and Holes in Semiconductors Bryan Ackland Department of Electrical and Computer Engineering Stevens Institute of Technology

More information

smal band gap Saturday, April 9, 2011

smal band gap Saturday, April 9, 2011 small band gap upper (conduction) band empty small gap valence band filled 2s 2p 2s 2p hybrid (s+p)band 2p no gap 2s (depend on the crystallographic orientation) extrinsic semiconductor semi-metal electron

More information

Semiconductors. Semiconductors also can collect and generate photons, so they are important in optoelectronic or photonic applications.

Semiconductors. Semiconductors also can collect and generate photons, so they are important in optoelectronic or photonic applications. Semiconductors Semiconducting materials have electrical properties that fall between true conductors, (like metals) which are always highly conducting and insulators (like glass or plastic or common ceramics)

More information

Semiconductor Device Physics

Semiconductor Device Physics 1 Semiconductor Device Physics Lecture 1 http://zitompul.wordpress.com 2 0 1 3 2 Semiconductor Device Physics Textbook: Semiconductor Device Fundamentals, Robert F. Pierret, International Edition, Addison

More information

KATIHAL FİZİĞİ MNT-510

KATIHAL FİZİĞİ MNT-510 KATIHAL FİZİĞİ MNT-510 YARIİLETKENLER Kaynaklar: Katıhal Fiziği, Prof. Dr. Mustafa Dikici, Seçkin Yayıncılık Katıhal Fiziği, Şakir Aydoğan, Nobel Yayıncılık, Physics for Computer Science Students: With

More information

CLASS 12th. Semiconductors

CLASS 12th. Semiconductors CLASS 12th Semiconductors 01. Distinction Between Metals, Insulators and Semi-Conductors Metals are good conductors of electricity, insulators do not conduct electricity, while the semiconductors have

More information

Charge Carriers in Semiconductor

Charge Carriers in Semiconductor Charge Carriers in Semiconductor To understand PN junction s IV characteristics, it is important to understand charge carriers behavior in solids, how to modify carrier densities, and different mechanisms

More information

Lecture 2. Semiconductor Physics. Sunday 4/10/2015 Semiconductor Physics 1-1

Lecture 2. Semiconductor Physics. Sunday 4/10/2015 Semiconductor Physics 1-1 Lecture 2 Semiconductor Physics Sunday 4/10/2015 Semiconductor Physics 1-1 Outline Intrinsic bond model: electrons and holes Charge carrier generation and recombination Intrinsic semiconductor Doping:

More information

Diamond. Covalent Insulators and Semiconductors. Silicon, Germanium, Gray Tin. Chem 462 September 24, 2004

Diamond. Covalent Insulators and Semiconductors. Silicon, Germanium, Gray Tin. Chem 462 September 24, 2004 Covalent Insulators and Chem 462 September 24, 2004 Diamond Pure sp 3 carbon All bonds staggered- ideal d(c-c) - 1.54 Å, like ethane Silicon, Germanium, Gray Tin Diamond structure Si and Ge: semiconductors

More information

Session 5: Solid State Physics. Charge Mobility Drift Diffusion Recombination-Generation

Session 5: Solid State Physics. Charge Mobility Drift Diffusion Recombination-Generation Session 5: Solid State Physics Charge Mobility Drift Diffusion Recombination-Generation 1 Outline A B C D E F G H I J 2 Mobile Charge Carriers in Semiconductors Three primary types of carrier action occur

More information

Semiconductor physics I. The Crystal Structure of Solids

Semiconductor physics I. The Crystal Structure of Solids Lecture 3 Semiconductor physics I The Crystal Structure of Solids 1 Semiconductor materials Types of solids Space lattices Atomic Bonding Imperfection and doping in SOLIDS 2 Semiconductor Semiconductors

More information

Ch. 2: Energy Bands And Charge Carriers In Semiconductors

Ch. 2: Energy Bands And Charge Carriers In Semiconductors Ch. 2: Energy Bands And Charge Carriers In Semiconductors Discrete energy levels arise from balance of attraction force between electrons and nucleus and repulsion force between electrons each electron

More information

Lecture (02) Introduction to Electronics II, PN Junction and Diodes I

Lecture (02) Introduction to Electronics II, PN Junction and Diodes I Lecture (02) Introduction to Electronics II, PN Junction and Diodes I By: Dr. Ahmed ElShafee ١ Agenda Current in semiconductors/conductors N type, P type semiconductors N Type Semiconductor P Type Semiconductor

More information

Electron Energy, E E = 0. Free electron. 3s Band 2p Band Overlapping energy bands. 3p 3s 2p 2s. 2s Band. Electrons. 1s ATOM SOLID.

Electron Energy, E E = 0. Free electron. 3s Band 2p Band Overlapping energy bands. 3p 3s 2p 2s. 2s Band. Electrons. 1s ATOM SOLID. Electron Energy, E Free electron Vacuum level 3p 3s 2p 2s 2s Band 3s Band 2p Band Overlapping energy bands Electrons E = 0 1s ATOM 1s SOLID In a metal the various energy bands overlap to give a single

More information

Contents CONTENTS. Page 2 of 47

Contents CONTENTS. Page 2 of 47 J. A. Hargreaves Lockerbie Academy June 2015 Contents CONTENTS Contents... 2 CHAPTER 7 CONDUCTORS, SEMICONDUCTORS AND INSULATORS... 4 Summary of Content... 4 Summary of this chapter- notes from column

More information

EE301 Electronics I , Fall

EE301 Electronics I , Fall EE301 Electronics I 2018-2019, Fall 1. Introduction to Microelectronics (1 Week/3 Hrs.) Introduction, Historical Background, Basic Consepts 2. Rewiev of Semiconductors (1 Week/3 Hrs.) Semiconductor materials

More information

Solar cells operation

Solar cells operation Solar cells operation photovoltaic effect light and dark V characteristics effect of intensity effect of temperature efficiency efficency losses reflection recombination carrier collection and quantum

More information

Introduction to Semiconductor Physics. Prof.P. Ravindran, Department of Physics, Central University of Tamil Nadu, India

Introduction to Semiconductor Physics. Prof.P. Ravindran, Department of Physics, Central University of Tamil Nadu, India Introduction to Semiconductor Physics 1 Prof.P. Ravindran, Department of Physics, Central University of Tamil Nadu, India http://folk.uio.no/ravi/cmp2013 Review of Semiconductor Physics Semiconductor fundamentals

More information

Fall 2014 Nobby Kobayashi (Based on the notes by E.D.H Green and E.L Allen, SJSU) 1.0 Learning Objectives

Fall 2014 Nobby Kobayashi (Based on the notes by E.D.H Green and E.L Allen, SJSU) 1.0 Learning Objectives University of California at Santa Cruz Electrical Engineering Department EE-145L: Properties of Materials Laboratory Lab 7: Optical Absorption, Photoluminescence Fall 2014 Nobby Kobayashi (Based on the

More information

ELECTRONIC I Lecture 1 Introduction to semiconductor. By Asst. Prof Dr. Jassim K. Hmood

ELECTRONIC I Lecture 1 Introduction to semiconductor. By Asst. Prof Dr. Jassim K. Hmood ELECTRONIC I Lecture 1 Introduction to semiconductor By Asst. Prof Dr. Jassim K. Hmood SOLID-STATE ELECTRONIC MATERIALS Electronic materials generally can be divided into three categories: insulators,

More information

Qualitative Picture of the Ideal Diode. G.R. Tynan UC San Diego MAE 119 Lecture Notes

Qualitative Picture of the Ideal Diode. G.R. Tynan UC San Diego MAE 119 Lecture Notes Qualitative Picture of the Ideal Diode G.R. Tynan UC San Diego MAE 119 Lecture Notes Band Theory of Solids: From Single Attoms to Solid Crystals Isolated Li atom (conducting metal) Has well-defined, isolated

More information

Free Electron Model for Metals

Free Electron Model for Metals Free Electron Model for Metals Metals are very good at conducting both heat and electricity. A lattice of in a sea of electrons shared between all nuclei (moving freely between them): This is referred

More information

Lecture 15: Optoelectronic devices: Introduction

Lecture 15: Optoelectronic devices: Introduction Lecture 15: Optoelectronic devices: Introduction Contents 1 Optical absorption 1 1.1 Absorption coefficient....................... 2 2 Optical recombination 5 3 Recombination and carrier lifetime 6 3.1

More information

Review of Semiconductor Fundamentals

Review of Semiconductor Fundamentals ECE 541/ME 541 Microelectronic Fabrication Techniques Review of Semiconductor Fundamentals Zheng Yang (ERF 3017, email: yangzhen@uic.edu) Page 1 Semiconductor A semiconductor is an almost insulating material,

More information

Semiconductor Devices and Circuits Fall Midterm Exam. Instructor: Dr. Dietmar Knipp, Professor of Electrical Engineering. Name: Mat. -Nr.

Semiconductor Devices and Circuits Fall Midterm Exam. Instructor: Dr. Dietmar Knipp, Professor of Electrical Engineering. Name: Mat. -Nr. Semiconductor Devices and Circuits Fall 2003 Midterm Exam Instructor: Dr. Dietmar Knipp, Professor of Electrical Engineering Name: Mat. -Nr.: Guidelines: Duration of the Midterm: 1 hour The exam is a closed

More information

Electronic Circuits for Mechatronics ELCT 609 Lecture 2: PN Junctions (1)

Electronic Circuits for Mechatronics ELCT 609 Lecture 2: PN Junctions (1) Electronic Circuits for Mechatronics ELCT 609 Lecture 2: PN Junctions (1) Assistant Professor Office: C3.315 E-mail: eman.azab@guc.edu.eg 1 Electronic (Semiconductor) Devices P-N Junctions (Diodes): Physical

More information

EE 346: Semiconductor Devices. 02/08/2017 Tewodros A. Zewde 1

EE 346: Semiconductor Devices. 02/08/2017 Tewodros A. Zewde 1 EE 346: Semiconductor Devices 02/08/2017 Tewodros A. Zewde 1 DOPANT ATOMS AND ENERGY LEVELS Without help the total number of carriers (electrons and holes) is limited to 2ni. For most materials, this is

More information

ITT Technical Institute ET215 Devices I Unit 1

ITT Technical Institute ET215 Devices I Unit 1 ITT Technical Institute ET215 Devices I Unit 1 Chapter 1 Chapter 2, Sections 2.1-2.4 Chapter 1 Basic Concepts of Analog Circuits Recall ET115 & ET145 Ohms Law I = V/R If voltage across a resistor increases

More information

Designing Information Devices and Systems II A. Sahai, J. Roychowdhury, K. Pister Discussion 1A

Designing Information Devices and Systems II A. Sahai, J. Roychowdhury, K. Pister Discussion 1A EECS 16B Spring 2019 Designing Information Devices and Systems II A. Sahai, J. Roychowdhury, K. Pister Discussion 1A 1 Semiconductor Physics Generally, semiconductors are crystalline solids bonded into

More information

So why is sodium a metal? Tungsten Half-filled 5d band & half-filled 6s band. Insulators. Interaction of metals with light?

So why is sodium a metal? Tungsten Half-filled 5d band & half-filled 6s band. Insulators. Interaction of metals with light? Bonding in Solids: Metals, Insulators, & CHEM 107 T. Hughbanks Delocalized bonding in Solids Think of a pure solid as a single, very large molecule. Use our bonding pictures to try to understand properties.

More information

Electronic Devices & Circuits

Electronic Devices & Circuits Electronic Devices & Circuits For Electronics & Communication Engineering By www.thegateacademy.com Syllabus Syllabus for Electronic Devices Energy Bands in Intrinsic and Extrinsic Silicon, Carrier Transport,

More information

Semiconductor Physics. Lecture 3

Semiconductor Physics. Lecture 3 Semiconductor Physics Lecture 3 Intrinsic carrier density Intrinsic carrier density Law of mass action Valid also if we add an impurity which either donates extra electrons or holes the number of carriers

More information

ECE 335: Electronic Engineering Lecture 2: Semiconductors

ECE 335: Electronic Engineering Lecture 2: Semiconductors Faculty of Engineering ECE 335: Electronic Engineering Lecture 2: Semiconductors Agenda Intrinsic Semiconductors Extrinsic Semiconductors N-type P-type Carrier Transport Drift Diffusion Semiconductors

More information

n N D n p = n i p N A

n N D n p = n i p N A Summary of electron and hole concentration in semiconductors Intrinsic semiconductor: E G n kt i = pi = N e 2 0 Donor-doped semiconductor: n N D where N D is the concentration of donor impurity Acceptor-doped

More information

Unit IV Semiconductors Engineering Physics

Unit IV Semiconductors Engineering Physics Introduction A semiconductor is a material that has a resistivity lies between that of a conductor and an insulator. The conductivity of a semiconductor material can be varied under an external electrical

More information

ECE 606 Homework Week 7 Mark Lundstrom Purdue University (revised 2/25/13) e E i! E T

ECE 606 Homework Week 7 Mark Lundstrom Purdue University (revised 2/25/13) e E i! E T ECE 606 Homework Week 7 Mark Lundstrom Purdue University (revised 2/25/13) 1) Consider an n- type semiconductor for which the only states in the bandgap are donor levels (i.e. ( E T = E D ). Begin with

More information

Electronic Devices And Circuits. Introduction

Electronic Devices And Circuits. Introduction Electronic Devices And Circuits Introduction An electronic device controls the movement of electrons. The study of electronic devices requires a basic understanding of the relationship between electrons

More information

Solar Cells Technology: An Engine for National Development

Solar Cells Technology: An Engine for National Development IOSR Journal of Electrical and Electronics Engineering (IOSR-JEEE) e-issn: 2278-1676,p-ISSN: 2320-3331, Volume 7, Issue 5 (Sep. - Oct. 2013), PP 13-18 Solar Cells Technology: An Engine for National Development

More information

Carrier Recombination

Carrier Recombination Notes for ECE-606: Spring 013 Carrier Recombination Professor Mark Lundstrom Electrical and Computer Engineering Purdue University, West Lafayette, IN USA lundstro@purdue.edu /19/13 1 carrier recombination-generation

More information

Review of Optical Properties of Materials

Review of Optical Properties of Materials Review of Optical Properties of Materials Review of optics Absorption in semiconductors: qualitative discussion Derivation of Optical Absorption Coefficient in Direct Semiconductors Photons When dealing

More information

SEMICONDUCTOR PHYSICS

SEMICONDUCTOR PHYSICS SEMICONDUCTOR PHYSICS by Dibyendu Chowdhury Semiconductors The materials whose electrical conductivity lies between those of conductors and insulators, are known as semiconductors. Silicon Germanium Cadmium

More information

The Periodic Table III IV V

The Periodic Table III IV V The Periodic Table III IV V Slide 1 Electronic Bonds in Silicon 2-D picture of perfect crystal of pure silicon; double line is a Si-Si bond with each line representing an electron Si ion (charge +4 q)

More information

Semiconductor Detectors

Semiconductor Detectors Semiconductor Detectors Summary of Last Lecture Band structure in Solids: Conduction band Conduction band thermal conductivity: E g > 5 ev Valence band Insulator Charge carrier in conductor: e - Charge

More information

EE 5211 Analog Integrated Circuit Design. Hua Tang Fall 2012

EE 5211 Analog Integrated Circuit Design. Hua Tang Fall 2012 EE 5211 Analog Integrated Circuit Design Hua Tang Fall 2012 Today s topic: 1. Introduction to Analog IC 2. IC Manufacturing (Chapter 2) Introduction What is Integrated Circuit (IC) vs discrete circuits?

More information

This is the 15th lecture of this course in which we begin a new topic, Excess Carriers. This topic will be covered in two lectures.

This is the 15th lecture of this course in which we begin a new topic, Excess Carriers. This topic will be covered in two lectures. Solid State Devices Dr. S. Karmalkar Department of Electronics and Communication Engineering Indian Institute of Technology, Madras Lecture - 15 Excess Carriers This is the 15th lecture of this course

More information

Electronic PRINCIPLES

Electronic PRINCIPLES MALVINO & BATES Electronic PRINCIPLES SEVENTH EDITION Chapter 2 Semiconductors Topics Covered in Chapter 2 Conductors Semiconductors Silicon crystals Intrinsic semiconductors Two types of flow Doping a

More information

Diodes. EE223 Digital & Analogue Electronics Derek Molloy 2012/2013.

Diodes. EE223 Digital & Analogue Electronics Derek Molloy 2012/2013. Diodes EE223 Digital & Analogue Electronics Derek Molloy 2012/2013 Derek.Molloy@dcu.ie Diodes: A Semiconductor? Conductors Such as copper, aluminium have a cloud of free electrons weak bound valence electrons

More information

EE 346: Semiconductor Devices

EE 346: Semiconductor Devices EE 346: Semiconductor Devices Lecture - 5 02/01/2017 Tewodros A. Zewde 1 The One-Electron Atom The potential function is due to the coulomb attraction between the proton and electron and is given by where

More information

Molecules and Condensed Matter

Molecules and Condensed Matter Chapter 42 Molecules and Condensed Matter PowerPoint Lectures for University Physics, Thirteenth Edition Hugh D. Young and Roger A. Freedman Lectures by Wayne Anderson Goals for Chapter 42 To understand

More information

Calculating Band Structure

Calculating Band Structure Calculating Band Structure Nearly free electron Assume plane wave solution for electrons Weak potential V(x) Brillouin zone edge Tight binding method Electrons in local atomic states (bound states) Interatomic

More information

Physics of Semiconductor Devices. Unit 2: Revision of Semiconductor Band Theory

Physics of Semiconductor Devices. Unit 2: Revision of Semiconductor Band Theory Physics of Semiconductor Devices Unit : Revision of Semiconductor Band Theory Unit Revision of Semiconductor Band Theory Contents Introduction... 5 Learning outcomes... 5 The Effective Mass... 6 Electrons

More information

ENERGY BANDS AND GAPS IN SEMICONDUCTOR. Muhammad Hafeez Javed

ENERGY BANDS AND GAPS IN SEMICONDUCTOR. Muhammad Hafeez Javed ENERGY BANDS AND GAPS IN SEMICONDUCTOR Muhammad Hafeez Javed www.rmhjaved.com rmhjaved@gmail.com Out Line Introduction Energy band Classification of materials Direct and indirect band gap of SC Classification

More information

Semiconductor Physics fall 2012 problems

Semiconductor Physics fall 2012 problems Semiconductor Physics fall 2012 problems 1. An n-type sample of silicon has a uniform density N D = 10 16 atoms cm -3 of arsenic, and a p-type silicon sample has N A = 10 15 atoms cm -3 of boron. For each

More information

Radiation Detection for the Beta- Delayed Alpha and Gamma Decay of 20 Na. Ellen Simmons

Radiation Detection for the Beta- Delayed Alpha and Gamma Decay of 20 Na. Ellen Simmons Radiation Detection for the Beta- Delayed Alpha and Gamma Decay of 20 Na Ellen Simmons 1 Contents Introduction Review of the Types of Radiation Charged Particle Radiation Detection Review of Semiconductor

More information

3C3 Analogue Circuits

3C3 Analogue Circuits Department of Electronic & Electrical Engineering Trinity College Dublin, 2014 3C3 Analogue Circuits Prof J K Vij jvij@tcd.ie Lecture 1: Introduction/ Semiconductors & Doping 1 Course Outline (subject

More information

Semiconductor Physics and Devices Chapter 3.

Semiconductor Physics and Devices Chapter 3. Introduction to the Quantum Theory of Solids We applied quantum mechanics and Schrödinger s equation to determine the behavior of electrons in a potential. Important findings Semiconductor Physics and

More information

Free Electron Model for Metals

Free Electron Model for Metals Free Electron Model for Metals Metals are very good at conducting both heat and electricity. A lattice of in a sea of electrons shared between all nuclei (moving freely between them): This is referred

More information

EXTRINSIC SEMICONDUCTOR

EXTRINSIC SEMICONDUCTOR EXTRINSIC SEMICONDUCTOR In an extrinsic semiconducting material, the charge carriers originate from impurity atoms added to the original material is called impurity [or] extrinsic semiconductor. This Semiconductor

More information

Practical 1P4 Energy Levels and Band Gaps

Practical 1P4 Energy Levels and Band Gaps Practical 1P4 Energy Levels and Band Gaps What you should learn from this practical Science This practical illustrates some of the points from the lecture course on Elementary Quantum Mechanics and Bonding

More information

Introduction to Engineering Materials ENGR2000. Dr.Coates

Introduction to Engineering Materials ENGR2000. Dr.Coates Introduction to Engineering Materials ENGR2000 Chapter 18: Electrical Properties Dr.Coates 18.2 Ohm s Law V = IR where R is the resistance of the material, V is the voltage and I is the current. l R A

More information

Basic cell design. Si cell

Basic cell design. Si cell Basic cell design Si cell 1 Concepts needed to describe photovoltaic device 1. energy bands in semiconductors: from bonds to bands 2. free carriers: holes and electrons, doping 3. electron and hole current:

More information

Practical 1P4 Energy Levels and Band Gaps

Practical 1P4 Energy Levels and Band Gaps Practical 1P4 Energy Levels and Band Gaps What you should learn from this practical Science This practical illustrates some of the points from the lecture course on Elementary Quantum Mechanics and Bonding

More information

Lecture (02) PN Junctions and Diodes

Lecture (02) PN Junctions and Diodes Lecture (02) PN Junctions and Diodes By: Dr. Ahmed ElShafee ١ I Agenda N type, P type semiconductors N Type Semiconductor P Type Semiconductor PN junction Energy Diagrams of the PN Junction and Depletion

More information

A semiconductor is an almost insulating material, in which by contamination (doping) positive or negative charge carriers can be introduced.

A semiconductor is an almost insulating material, in which by contamination (doping) positive or negative charge carriers can be introduced. Semiconductor A semiconductor is an almost insulating material, in which by contamination (doping) positive or negative charge carriers can be introduced. Page 2 Semiconductor materials Page 3 Energy levels

More information

LEC E T C U T R U E R E 17 -Photodetectors

LEC E T C U T R U E R E 17 -Photodetectors LECTURE 17 -Photodetectors Topics to be covered Photodetectors PIN photodiode Avalanche Photodiode Photodetectors Principle of the p-n junction Photodiode A generic photodiode. Photodetectors Principle

More information

Classification of Solids

Classification of Solids Classification of Solids Classification by conductivity, which is related to the band structure: (Filled bands are shown dark; D(E) = Density of states) Class Electron Density Density of States D(E) Examples

More information

5. Semiconductors and P-N junction

5. Semiconductors and P-N junction 5. Semiconductors and P-N junction Thomas Zimmer, University of Bordeaux, France Summary Learning Outcomes... 2 Physical background of semiconductors... 2 The silicon crystal... 2 The energy bands... 3

More information

Photodiodes and other semiconductor devices

Photodiodes and other semiconductor devices Photodiodes and other semiconductor devices Chem 243 Winter 2017 What is a semiconductor? no e - Empty e levels Conduction Band a few e - Empty e levels Filled e levels Filled e levels lots of e - Empty

More information

Semiconductor-Detectors

Semiconductor-Detectors Semiconductor-Detectors 1 Motivation ~ 195: Discovery that pn-- junctions can be used to detect particles. Semiconductor detectors used for energy measurements ( Germanium) Since ~ 3 years: Semiconductor

More information

Chapter 1 Overview of Semiconductor Materials and Physics

Chapter 1 Overview of Semiconductor Materials and Physics Chapter 1 Overview of Semiconductor Materials and Physics Professor Paul K. Chu Conductivity / Resistivity of Insulators, Semiconductors, and Conductors Semiconductor Elements Period II III IV V VI 2 B

More information

Concept of Core IENGINEERS- CONSULTANTS LECTURE NOTES SERIES ELECTRONICS ENGINEERING 1 YEAR UPTU. Page 1

Concept of Core IENGINEERS- CONSULTANTS LECTURE NOTES SERIES ELECTRONICS ENGINEERING 1 YEAR UPTU. Page 1 Concept of Core Conductivity of conductor and semiconductor can also be explained by concept of Core. Core: Core is a part of an atom other than its valence electrons. Core consists of all inner shells

More information

Solid State Device Fundamentals

Solid State Device Fundamentals Solid State Device Fundamentals ENS 345 Lecture Course by Alexander M. Zaitsev alexander.zaitsev@csi.cuny.edu Tel: 718 982 2812 Office 4N101b 1 The free electron model of metals The free electron model

More information

Advantages / Disadvantages of semiconductor detectors

Advantages / Disadvantages of semiconductor detectors Advantages / Disadvantages of semiconductor detectors Semiconductor detectors have a high density (compared to gas detector) large energy loss in a short distance diffusion effect is smaller than in gas

More information

Lecture 3b. Bonding Model and Dopants. Reading: (Cont d) Notes and Anderson 2 sections

Lecture 3b. Bonding Model and Dopants. Reading: (Cont d) Notes and Anderson 2 sections Lecture 3b Bonding Model and Dopants Reading: (Cont d) Notes and Anderson 2 sections 2.3-2.7 The need for more control over carrier concentration Without help the total number of carriers (electrons and

More information

Direct and Indirect Semiconductor

Direct and Indirect Semiconductor Direct and Indirect Semiconductor Allowed values of energy can be plotted vs. the propagation constant, k. Since the periodicity of most lattices is different in various direction, the E-k diagram must

More information

Chem 481 Lecture Material 3/20/09

Chem 481 Lecture Material 3/20/09 Chem 481 Lecture Material 3/20/09 Radiation Detection and Measurement Semiconductor Detectors The electrons in a sample of silicon are each bound to specific silicon atoms (occupy the valence band). If

More information

CME 300 Properties of Materials. ANSWERS: Homework 9 November 26, As atoms approach each other in the solid state the quantized energy states:

CME 300 Properties of Materials. ANSWERS: Homework 9 November 26, As atoms approach each other in the solid state the quantized energy states: CME 300 Properties of Materials ANSWERS: Homework 9 November 26, 2011 As atoms approach each other in the solid state the quantized energy states: are split. This splitting is associated with the wave

More information

Mat E 272 Lecture 25: Electrical properties of materials

Mat E 272 Lecture 25: Electrical properties of materials Mat E 272 Lecture 25: Electrical properties of materials December 6, 2001 Introduction: Calcium and copper are both metals; Ca has a valence of +2 (2 electrons per atom) while Cu has a valence of +1 (1

More information