DOCSLIB.ORG

Effect of Adding Selected Impurities the Optical and Electrical Properties of Silicon

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Effect of Adding Selected Impurities the Optical and Electrical Properties of Silicon Effect of Adding Selected Impurities the Optical and Electrical Properties of Silicon Mohamed Osman Ahmed Ibrahim Postgraduate Diploma in Physics-University of Gezira (2014) B.Sc. in Education physics &mathematics, University of Gezira (2012) A Dissertation Submitted to the University of Gezira in Partial Fulfillment of the Requirements for the Award of the Degree of Master of Science in Physics Sciences Department of Electronics Engineering Faculty of Engineering and Technology May, 2018 i Effect of Adding Selected Impurities the Optical and Electrical Properties of Silicon Mohamed Osman Ahmed Ibrahim Supervision Committee: Name Position Signature Dr. Hasaballrasoul Gesmallh Ismail Main Supervisor ……………. Prof. Mubarak Dirar Abdullah Yagoup Co. Supervisor …………..... April /2018 ii Effect of Adding Selected Impurities the Optical and Electrical Properties of Silicon Mohamed Osman Ahmed Ibrahim Examination Committee: Name Position Signature Dr. Hasaballrasoul Gesmallh Ismail Chairperson ………....... Dr. Nooreldain Edriss Fadol Adam External Examiner …………... Dr. Murtada Mohammed Abdelwahab Internal Examiner …………... Date of Examination: 28/April, 2018. iii Holly Quran قَاَل تَ َعاََل: م آ آ م آ ﴿يرفَ آ َنُ َ ني َ َ ُ َ ُ َ ني َ آ ٍ آ أُ تُ َ َ ع ل َ َدَرَجات َنُ مباتَعَملُ َن َخبريٌ ﴾ سورةالمجادلة ﴿11﴾ iv Dedication To those who taught me how to catch the pen a speak to my mother Who taught me contestation My father My brothers To my teachers my friends My colleagues in the study To Family of department of physics &mathematics, Faculty of Education –El Hasaheisa, University of Gezira to all those who are the source of their nation`s progress. v Acknowledgements Thanks to the University of Gezira, college of Engineering and technology, especially the electronics department that we have and to Dr. Hasaballrasoul Gesmallh Ismail Professor Mubarak Dirar Abdullah "University of Sudan", Dr. Mohammed Saeed Dawalbait and Dr. Murtada Abdul Wahab Mohammed "University of Gezira. Dr. Abdalsaki University of Elnileen. vi Effect of Adding Selected Impurities the Optical and Electrical Properties of Silicon Mohamed Osman Ahmed Ibrahim M.Sc. in Physics Abstract The Impurities are used to improve optical and electrical properties for semiconductor, in this piece of study impurities are used to improve the optical and electrical properties of a silicon semiconductor. The aim of this study effect of adding impurities to improve the optical and electrical properties of silicon. For this reason three different samples are prepared from silicon doped with different types of impurities having the different concentration. One sample is doped with iodine pointedly (1.03%), another one is doped with Coumarin 500 pointedly (1.05%) and the third one is doped with Rohdamin B pointedly (1.07%). Spectrometer is used to measure absorption, absorption coefficient, extintion coefficient, and energy gap each of the above three mentioned samples. The results showed that for absorption the maximum is absorbed in the case of iodine sample and the minimum is in the case of the Coumarin 500 while the absorption of the Rohdamin B is found to lie in between that of these two samples. For the absorption coefficient the results showed that the maximum is in the case of the Rohdamin B sample and the minimum is for the Coumarin 500 sample while the coefficient of absorption for the iodine sample is found to lie in between that of these two samples. As for the excitation coefficient it is found that the maximum occurred in the case of the Rohdamin B sample and the minimum is in the case of the Coumarin 500 sample while that for the iodine sample is found to lie in between that of the above two cases. Finally the results of measurements of the energy gap are found to be 2.11 ev for the Coumarin 500 sample, 2.08 ev for the iodine sample, 2.03 ev for the Rohdamin B sample. The outcome of the results found in this piece of study indicate that the energy gap and the absorption increase of the three doped samples. However, the absorption coefficient and excitation coefficient are found to depend on the type of the impurity used. Here they are found to increase in the case of the iodine and Rohdamin B impurities and to decrease in the case of Coumarin 500. This study recommends to use same types of impurities added to anther semiconductor like germanium having the same concentration used have so as to see whether the results obtained here constitute a general rule or they just a special singular case. vii أثر تغيير إضافة الشوائب في تحسين الصفات الضوئية والكهربية للسليكون محمد عثمان أحمد إبراهيم ماجستير العلوم في الفيزياء ملخص الدراسة الشووووووها ا لدووووووو ال ووووووو ة علوووووووى تحسوووووووات الضوووووو ال وووووووه اة والكدرب اوووووووة ﻷشوووووووو ﻻ ال ه ووووووو . فووووووا جوووووواا السووووووائ ووووووت ال ا ووووووة الشووووووها ا تسووووووكو لكحسووووووات الضوووووو ال ووووووه اة والكدرباووووووة للسوووووولاكه شووووووو ال ه ووووو . والدووووو ا وووووت ال ا وووووة ا وووووة تووووور صفووووو فة الشوووووها ا فوووووا تحسوووووات الضووووو ال وووووه اة والكدرباوووووة للسووووولاكه . لدووووواا السووووووا توووووا تح وووووار تووووو ن عاوووووو وكل وووووة وووووت السووووولاكه وشوووووهب بووووو ها وكل ووووووة ووووووت الشووووووها ا بكرا اووووووا وكل ووووووة. ال اوووووووة اﻷولووووووى شووووووهب ب وضوووووور الاووووووه بكر اووووووا 1.03%(، وال اوووووووة الش اووووووة شووووووهب ب وضوووووور الكووووووه ر ت 500بكر اووووووا %1.05(، وال اوووووووة الش لشووووووة شووووووهب ب وضوووووور الووووووووووورو ا ات بكر اوووووووووووا %1.07(. وجدووووووووووو إ اووووووووووو ا وووووووووووه ص بوووووووووووا 2000 سوووووووووووكو ل اووووووووووو اﻹ كضووووووو ، ووووووو اﻹ كضووووووو ، ووووووو الكوووووووهجات، وفسوووووووهة ال نوووووووة لل اوووووووو ال وووووووا ه ة عووووووو ﻻ. الوكووووووو وفوووووووح علوووووووى ص كضووووووو ووووووو لل اووووووووة ال شوووووووهبة ب وضووووووورالاه و نووووووو نا وووووووو لل اووووووووة ال شووووووهبة ب وضوووووور الكووووووه ر ت 500، باو وووووو اﻹ كضوووووو ل اوووووووة الوووووورو ا ات وجوووووو فووووووا ال وووووو بووووووات ال اوكووووووات عوووووو ﻻ. ل وووووو اﻹ كضوووووو الوكوووووو وفووووووح علووووووى نا ووووووة فووووووا لووووووة ال اوووووووة ال شووووووهبو ب وضووووور الووووورو ا ات و نووووو نا وووووة فوووووا لوووووة ال اووووووة ال شوووووهبو ب وضووووور الكوووووه ر ت 500 باو ووووو لل اووووووة ال شوووووهبو ب وضووووور الاوووووه وجووووو بوووووات ال اوكوووووات عووووو ﻻ. ب لوسووووووة ل ووووو الكوووووهجات وجووووو علوووووا نا وووووة لوووووو فوووووا ال اووووووة ال شوووووهبة ب وضووووور الووووورو ا ات و نووووو نا وووووة لل اووووووة ال شوووووهبة ب وضووووور الكوووووه ر ت 500 باو ووووو لل اووووووة ال شوووووهبو ب وضووووور الاوووووه وجووووو فوووووا ال ووووو بوووووات ال اوكوووووات عووووو ﻻ. اووووورا كووووو نا ووووو فسووووووووووهة ال نووووووووووة وووووووووو 2.11 صلككوووووووووورو فهلوووووووووو لل اوووووووووووة ال شووووووووووهبو ب وضوووووووووور الكووووووووووه ر ت 500، 2.08صلككوووووووورو فهلوووووووو لل اوووووووووة ال شووووووووهبو ب وضوووووووور الاووووووووه و2.03 صلككوووووووورو فهلوووووووو لل اوووووووووة ال شووووووووهبو ل وضووووور الووووورو ا ات . ورجووووو جووووواﻻ السا اوووووو وووووت ال ا وووووو وجووووو دووووو تشوووووار صلوووووى فسوووووهة ال نوووووو واﻹ كضووووووو ا ووووووو ا فوووووووا لوووووووة الش توووووووة عاوووووووو ال شوووووووهبة، باو ووووووو ووووووو اﻹ كضووووووو و ووووووو الكووووووهجات وجوووووو د وووووو ك وووووو ا علووووووا هعاووووووة الشووووووها ا ال سووووووكو و اوووووو د وووووو ا وووووو ا فووووووا لووووووة الكشووووووه ا بوووووو لاه والوووووورو ا ات وت وووووو فووووووا لووووووة الكووووووه ر ت 500. جوووووواﻻ ال ا ووووووة ته ووووووا ب ووووووكو ا وووووو الشوووووها ا وصفووووو فكد لشووووووو ه ووووو ووووور لسر ووووو اه بوووووو و الكرا اوووووا ل رفوووووة جووووو جووووواﻻ الوكووووو ال ة ت كور ن ع ة ع و لة ة ب لسلاكه . viii Table of Contents NO Subject page 1 Halley Quran iv 2 Dedication v 3 Acknowledgment vi 6 English Abstract vii 7 Arabic Abstract viii 8 Table of Contents ix 9 List of Figures xi 10 List of Abbreviations xii Chapter One Introduction 1.1 Overview 1 1.2 A study Problem 2 1.3 Aims of research 3 1.4 Methodology 3 1.5 Lay out of these 3 Chapter Two Literature Review 2.1 Introduction 4 2.2 Semiconductor 4 2.3 Semiconductor types 4 2.4 Semiconductor devices 6 2.5 Energy bands and electrical conduction 10 2.6 Conductivity 21 2.7 Impurities 23 2.8 Doping of Semiconductor 25 2.9 Silicon 26 2.10 Absorption 28 ix 2.11 Absorption Coefficients 28 2.12 Determination Of Band Gaps 29 2.13 Literature Review 29 Chapter Three Material and Method 3.1 Material 32 3.1.1 Iodine 32 3.1.2 Coumarine500 32 3.1.3 Rohdamin B 32 3.1.4 Spin Coating 32 3.1.5 USB2000 33 3.2 Methods 33 Chapter Four Results and Discussion 4.1 Results 35 4.2 Discussion 37 Chapter Five Conclusion and Recommendations 5.1 Conclusion 39 5.2 Recommendation 39 5.3 Reference 40 x List of Figures No Figures Page 2.1 Fermi levels to metal, semimetal, semiconductor and insulator 10 2.2 Two-dimensional representation of the silicon lattice 18 2.3 (a) Donor and (b) acceptor levels in extrinsic semiconductors 19 2.4 Schematic representation of the number of electrons per cubic 20 centimeter in the conduction band versus temperature for an extrinsic semiconductor with low doping 2.5 Conductivity of two extrinsic semiconductor 21 3.1 USB 2000 spectrometer 33 4.1 relationship between absorbance and wavelength 35 4.2 the relation between the Absorption coefficient and 35 wavelengths 4.3 the relation between the Excitation coefficient and wavelengths 36 4.4 relationship between ( (αhf)² ev. m⁻ ¹ and (hf) ev) 36 xi List of Abbreviations Abbreviation Full name ICs Integrated circuits. LED Light Emitting Diode USB Universal Serial Bus xii Chapter One Introduction 1.1 Overview A semiconductor material has an electrical conductivity value falling between that of a conductor, such as copper, and an insulator, such as glass. Their resistance decreases as their temperature increases, which is behavior opposite to that of a metal.
Load more

Recommended publications
  • Iii-Nitride Ultraviolet Light-Emitting Diodes: Approaches for the Enhanced Efficiency
    Copyright Warning & Restrictions The copyright law of the United States (Title 17, United States Code) governs the making of photocopies or other reproductions of copyrighted material. Under certain conditions specified in the law, libraries and archives are authorized to furnish a photocopy or other reproduction. One of these specified conditions is that the photocopy or reproduction is not to be “used for any purpose other than private study, scholarship, or research.” If a, user makes a request for, or later uses, a photocopy or reproduction for purposes in excess of “fair use” that user may be liable for copyright infringement, This institution reserves the right to refuse to accept a copying order if, in its judgment, fulfillment of the order would involve violation of copyright law. Please Note: The author retains the copyright while the New Jersey Institute of Technology reserves the right to distribute this thesis or dissertation Printing note: If you do not wish to print this page, then select “Pages from: first page # to: last page #” on the print dialog screen The Van Houten library has removed some of the personal information and all signatures from the approval page and biographical sketches of theses and dissertations in order to protect the identity of NJIT graduates and faculty. ABSTRACT III-NITRIDE ULTRAVIOLET LIGHT-EMITTING DIODES: APPROACHES FOR THE ENHANCED EFFICIENCY by Moulik Patel III-nitride ultraviolet (UV) light-emitting diodes (LEDs) offer marvelous potential for a wide range of applications, including air/water purification, surface disinfection, biochemical sensing, cancer cell elimination, and many more. III-nitride semiconductor alloys, especially AlGaN and AlInN, have drawn significant attention due to their significant advantages that include environmental-friendly material composition, compact in size, longer lifetime, low power consumption, and tunable optical emission.
    [Show full text]
  • Sudan University of Science and Technology College of Graduate Studies
    Sudan University of Science and Technology College of Graduate Studies Increasing The Electrical Conductivity of the semiconductor by Doping and Heating زﯾﺎدة اﻟﻤﻮﺻﻠﯿﺔ اﻟﻜﮭﺮﺑﯿﺔ ﻻﺷﺒﺎه اﻟﻤﻮﺻﻼت ﺑﺎﻟﺘﺸﻮﯾﺐ و اﻟﺤﺮارة Thesis Submitted For Partial Fulfillment of the Requirement for Degree of Master in Physics Prepared by : Seddega Mohammed Noor Diab Supervised by : Dr. Ahmed ELhassan ELfaki December 2016 1 اﻵﯾــــــــــــــــــﺔ ﻗﺎل ﺗﻌﺎﻟﻰ: ﺑﺳم اﻟﻠﮫ اﻟرﺣﻣن اﻟرﺣﯾم ﯾُﻜَﻠّ ِﻒُ اﻟﻠﱠﮫُ (ﻧَﻔْﺴًﺎ ﻻ َإِﻻ ﱠ وُﺳْﻌَﮭَﺎ ﻟَﮭَﺎ ﻣَﺎ ﻛَﺴَﺒَﺖْ و َﻋَﻠَﯿْﮭَﺎ ﻣَﺎ اﻛْﺘَﺴَﺒَﺖْ رَﺑﱠﻨَﺎ ﻻ َ ﻧﱠﺴِﯿﻨَﺎ أَوْ ﺗُﺆَاﺧِﺬْﻧَﺎ أَﺧْﻄَﺄ إِن ْﻧَﺎ رَﺑﱠﻨَﺎ و َﻻ َ ﺗَﺤْﻤِﻞْ ﻋَﻠَﯿْﻨَﺎ إِﺻْﺮًا ﻛَﻤَﺎ ﺣَﻤَﻠْﺘَﮫُ ﻋَﻠَﻰ َ ﻣِﻦ ﻗَﺒْﻠِﻨَﺎ رَﺑﱠﻨَﺎاﻟ و ﱠﺬِﯾﻦَﻻ َ ﺗُﺤَﻤِّﻠْﻨَﺎ ﻣَﺎ ﻻ َ طَﺎﻗَﺔَ ﻟَﻨَﺎ ﺑِﮫِ و َاﻋْﻒُ ﻋَﻨﱠﺎ و َاﻏْﻔِﺮْ ﻟَﻨَﺎ و َارْﺣَﻤْﻨَﺎ أَﻧﺖَ ﻣَﻮْﻻ َ ﻧَﺎ ﻓَﺎﻧﺼُﺮْﻧَﺎ ﻋَﻠَﻰ ﻘَﻮْمِاﻟْ اﻟْﻜَﺎﻓِﺮ ِﯾﻦَ ) ﺻدق اﻟﻠﮫ اﻟﻌظﯾم ﺳورة اﻟﺑﻘرة اﻷﯾﺔ (286) Dedication To whom he strives to bless comfort and welfare and never stints what he owns to push me in the success way who I taught me to promote life stairs wisely and patiently, to my dearest father To the Spring that never stops giving, to my mother who weaves my happiness with strings from her merciful heart To whose love flows in my veins, and my heart always remembers them, to my brothers ,sisters and my fiends To those who taught us letters of gold and words of jewel of the utmost and sweetest sentences in the whole knowledge. Who reworded to us their knowledge simply and from their thoughts made a lighthouse guides us through the knowledge and success path, To our honored teachers and professors.
    [Show full text]
  • Introduction to Semiconductor
    Introduction to semiconductor Semiconductors: A semiconductor material is one whose electrical properties lie in between those of insulators and good conductors. Examples are: germanium and silicon. In terms of energy bands, semiconductors can be defined as those materials which have almost an empty conduction band and almost filled valence band with a very narrow energy gap (of the order of 1 eV) separating the two. Types of Semiconductors: Semiconductor may be classified as under: a. Intrinsic Semiconductors An intrinsic semiconductor is one which is made of the semiconductor material in its extremely pure form. Examples of such semiconductors are: pure germanium and silicon which have forbidden energy gaps of 0.72 eV and 1.1 eV respectively. The energy gap is so small that even at ordinary room temperature; there are many electrons which possess sufficient energy to jump across the small energy gap between the valence and the conduction bands. 1 Alternatively, an intrinsic semiconductor may be defined as one in which the number of conduction electrons is equal to the number of holes. Schematic energy band diagram of an intrinsic semiconductor at room temperature is shown in Fig. below. b. Extrinsic Semiconductors: Those intrinsic semiconductors to which some suitable impurity or doping agent or doping has been added in extremely small amounts (about 1 part in 108) are called extrinsic or impurity semiconductors. Depending on the type of doping material used, extrinsic semiconductors can be sub-divided into two classes: (i) N-type semiconductors and (ii) P-type semiconductors. 2 (i) N-type Extrinsic Semiconductor: This type of semiconductor is obtained when a pentavalent material like antimonty (Sb) is added to pure germanium crystal.
    [Show full text]
  • XI. Band Theory and Semiconductors I
    XI. ELECTRONIC PROPERTIES (DRAFT) 11.1 THE ALLOWED ENERGIES OF ELECTRONS Over the next few weeks we are going to explore the electrical properties of materials. Our starting point for this investigation is simply to ask the question, “Why do some materials conduct electricity and others don’t?” It should come as no surprise that the answer to this question can be found in structure, in this case the structure of the electrons density, which in turn is related to the electron energies and how these may change when a material is subjected to an electrical potential difference, i.e., hooked up to a battery. Up until the early part of the twentieth century it was thought that electrons obeyed the laws of classical mechanics, and, just like everything we could observe at that time, an electron could be made to move in a way that it would take on any energy we wished. For example, if we want a ball with the mass of 0.25 kg to have a kinetic energy of 0.5 J, all we need do is accelerate it to exactly 2 m/sec. If we want its kinetic energy to be 0.501 J, then we need to accelerate it to 2.001999 m/sec. If we want it to have a kinetic energy of X, it must have a velocity of exactly (8X)1/2. According to the principles of classical mechanics, there is nothing that prevents us from doing this. However, it turns out that these principles are not quite right, under some circumstances the ball cannot be made to take on any energy we desire, it can only possess specific energies, which we often denote with a subscript, En.
    [Show full text]
  • CHAPTER 1: Semiconductor Materials & Physics
    Chapter 1 1 CHAPTER 1: Semiconductor Materials & Physics In this chapter, the basic properties of semiconductors and microelectronic devices are discussed. 1.1 Semiconductor Materials Solid-state materials can be categorized into three classes - insulators, semiconductors, and conductors. As shown in Figure 1.1, the resistivity of semiconductors, ρ, is typically between 10-2 and 108 Ω-cm. The portion of the periodic table related to semiconductors is depicted in Table 1.1. Figure 1.1: Typical range of conductivities for insulators, semiconductors, and conductors. Semiconductors can be composed of a single element such as silicon and germanium or consist of two or more elements for compound semiconductors. A binary III-V semiconductor is one comprising one element from Column III (such as gallium) and another element from Column V (for instance, arsenic). The common element and compound semiconductors are displayed in Table 1.2. City University of Hong Kong Chapter 1 2 Table 1.1: Portion of the Periodic Table Related to Semiconductors. Period Column II III IV V VI 2 B C N Boron Carbon Nitrogen 3 Mg Al Si P S Magnesium Aluminum Silicon Phosphorus Sulfur 4 Zn Ga Ge As Se Zinc Gallium Germanium Arsenic Selenium 5 Cd In Sn Sb Te Cadmium Indium Tin Antimony Tellurium 6 Hg Pd Mercury Lead Table 1.2: Element and compound semiconductors. Elements IV-IV III-V II-VI IV-VI Compounds Compounds Compounds Compounds Si SiC AlAs CdS PbS Ge AlSb CdSe PbTe BN CdTe GaAs ZnS GaP ZnSe GaSb ZnTe InAs InP InSb City University of Hong Kong Chapter 1 3 1.2 Crystal Structure Most semiconductor materials are single crystals.
    [Show full text]
  • Electrical Properties View of an Integrated Circuit Electrical Conduction Electrical Properties
    4/28/15 Electrical Properties View of an Integrated Circuit • Scanning electron micrographs of an IC: ISSUES TO ADDRESS... Al (d) • How are electrical conductance and resistance Si characterized? (What effects conductance?) (doped) 45 µm 0.5 mm • What are the physical phenomena that distinguish conductors, semiconductors, and insulators? • A dot map showing location of Si (a semiconductor): • For metals, how is conductivity affected by -- Si shows up as light regions. (b) imperfections, temperature, and deformation? & dark region is Al wiring • For semiconductors, how is conductivity affected by impurities (doping) and temperature? 2 Chapter 18 - 1 Chapter 18 - Electrical Conduction Electrical Properties • Ohm's Law: V = I R • Which will have the greater resistance? voltage drop (volts = J/C) resistance (Ohms) current (amps = C/s) C = Coulomb 2 2ρ 8ρ R D 1 = 2 = 2 !D$ πD • Resistivity, ρ: π # & " 2 % - a material property that is independent of sample size and geometry current flow € ρ ρ R 2D R = = = 1 path length 2 2 2 !2D$ πD 8 cross-sectional area π # & " 2 % of current flow € RA ρ = • Analogous to flow of cars on road • Resistance depends on sample geometry and • Conductivity, σ 1 size. σ = ρ • Resistivity of independent of sample geometry Chapter 18 - 3 Chapter 18 - 4 1 4/28/15 Conductivity: Comparison Definitions Room temperature values in (Ω - m)-1 Further definitions METALS conductors CERAMICS J = σ ε ß another way to state Ohm’s law Silver 6.8 x 10 7 Soda-lime glass 10 -10-10 -11 7 -9 current I Copper 6.0 x 10 Concrete 10 J = current density = = like a flux 7 surface area A Iron 1.0 x 10 Aluminum oxide <10-13 ε = electric field potential = V/ℓ € SEMICONDUCTORS POLYMERS J = σ (V/ℓ ) -14 Silicon 4 x 10 -4 Polystyrene <10 0 -15 -17 Electron flux conductivity voltage gradient Germanium 2 x 10 Polyethylene 10 -10 GaAs 10 -6 semiconductors insulators 6 Chapter 18 - 5 Selected values from Tables 18.1, 18.3, and 18.4, Callister & Rethwisch 9e.
    [Show full text]
  • Bipolar Junction Transistor As a Switch
    IOSR Journal of Electrical and Electronics Engineering (IOSR-JEEE) e-ISSN: 2278-1676,p-ISSN: 2320-3331, Volume 13, Issue 1 Ver. I (Jan. – Feb. 2018), PP 52-57 www.iosrjournals.org Bipolar Junction Transistor as a Switch Ali Habeb Aseeri1, Fouzeyah Rajab Ali2 1(Switching Dep, High institute of telecommunication and navigation/PAAET, Kuwait,[email protected]) 2(Switching Dep, High institute of telecommunication and navigation/PAAET, Kuwait,[email protected]) Abstract: Understanding the application of a bipolar Junction transistor or BJT as a switch requiers understanding the general working principles behind a transistor and the specific working principles behind a BJT. A transistor is essentially a semiconductor device with physical properties that make it ideal for amplifying or switching electric current and other signal. At the heart of this device is a doped semiconductor with engineered properties to alter its conductivity for a particular use. A BJT is a type of transistor with two major semiconductor materials that constitute three major areas or regions, each doped according to requirements. This architectural characteristics of a BJT brings forth effective applications in implications or on-off switching operations. Nonetheless, understanding BJT as a switch requires understanding the working principles underneath the device, the functions of each of the three major regions within this transistor, and the role of electron movement or current flow in the switching mechanism Keywords: BJT-collector-emitter-base-collector voltage
    [Show full text]
  • Lecture 7: Extrinsic Semiconductors - Fermi Level
    Lecture 7: Extrinsic semiconductors - Fermi level Contents 1 Dopant materials 1 2 EF in extrinsic semiconductors 5 3 Temperature dependence of carrier concentration 6 3.1 Low temperature regime (T < Ts)................7 3.2 Medium temperature regime (Ts < T < Ti)...........8 1 Dopant materials Typical doping concentrations in semiconductors are in ppm (10−6) and ppb (10−9). This small addition of `impurities' can cause orders of magnitude increase in conductivity. The impurity has to be of the right kind. For Si, n-type impurities are P, As, and Sb while p-type impurities are B, Al, Ga, and In. These form energy states close to the conduction and valence band and the ionization energies are a few tens of meV . Ge lies the same group IV as Si so that these elements are also used as impurities for Ge. The ionization energy data n-type impurities for Si and Ge are summarized in table 1. The ionization energy data for p-type impurities for Si and Ge is summarized in table 2. The dopant ionization energies for Ge are lower than Si. Ge has a lower band gap (0.67 eV ) compared to Si (1.10 eV ). Also, the Table 1: Ionization energies in meV for n-type impurities for Si and Ge. Typical values are close to room temperature thermal energy. Material P As Sb Si 45 54 39 Ge 12 12.7 9.6 1 MM5017: Electronic materials, devices, and fabrication Table 2: Ionization energies in meV for p-type impurities. Typical values are comparable to room temperature thermal energy.
    [Show full text]
  • Electron Devices Extrinsic Semiconductor
    ECE201 – ELECTRON DEVICES EXTRINSIC SEMICONDUCTOR PRESENTED BY K.PANDIARAJ ECE DEPARTMENT KALASALINGAM UNIVERSITY PREVIOUS CLASS TOPICS • Introduction to semiconductors • Hole • Intrinsic semiconductor • Covalent bonding • Electron and hole current • Conduction in intrinsic semi conductor • Conventional current • Intrinsic carrier concentration • Fermi level in intrinsic semiconductor REVIEW QUESTIONS • How are covalent bonds formed? • What is meant by the term intrinsic? • Effectively, how many valance electrons are there in each atom within a silicon crystal? • Are free electrons in the valance band or in the conduction band? • Which electrons are responsible for current in a material? • What is hole? EXTRINSIC SEMICONDUCTOR • Introduction • The semiconductor in which impurities are added is called extrinsic semiconductor. • When the impurities are added to the intrinsic semiconductor, it becomes an extrinsic semiconductor. • The process of adding impurities to the semiconductor is called doping. Doping increases the electrical conductivity of semiconductor. • Extrinsic semiconductor has high electrical conductivity than intrinsic semiconductor. Hence the extrinsic semiconductors are used for the manufacturing of electronic devices such as diodes, transistors etc. • The number of free electrons and holes in extrinsic semiconductor are not equal. EXTRINSIC SEMICONDUCTOR Types of impurities • Two types of impurities are added to the semiconductor. They are pentavalent and trivalent impurities. Pentavalent impurities • Pentavalent impurity atoms have 5 valence electrons. The various examples of pentavalent impurity atoms include phosphorus (P), arsenic (as), antimony (sb), etc. The atomic structure of pentavalent atom (phosphorus) and trivalent atom (boron) is shown in below fig. EXTRINSIC SEMICONDUCTOR • Phosphorus atom has 15 electrons (2 electrons in first orbit, 8 electrons in second orbit and 5 electrons in the outermost orbit).
    [Show full text]
  • Unit 14 Semiconductor Physics
    UNIT 14 SEMICONDUCTOR PHYSICS Structure Introduction Objectives Energy Bands in Solids Intrinsic and Extrinsic Semiconductors Conduction in Intrinsic Semiconductors Extrinsic Semiconductors p-n Junction Diode p-n Junction with no External Voltage Characteristics of Forward and Reverse Bias Diode as a Rectifier Other Applications of Diodes Solar Cell Photodiode Light Emitting Diode Zener Diode Summary Terminal Questions . Solutions and Answers 14.1 INTRODUCTION We are all familiar with simple applications of electronics like radio, television, calculators, personal computers etc. in, our day-to-day lives. If we look inside any electronic equipment, we will find resistors, capacitors, semiconductor diodes, transistors etc. Semiconductors have contributed immensely to the developments in science and technology. The invention of transistors in 1940s and that of integrated circuits (ICs) later led to great advancements in the capabilities of electronic devices and a wide variety of applications in different walks of life. 'This is because electronic components made up of se~niconductormaterials have advantages such as higher reliability, low power requirement and miniaturisation of devices. With recent semiconductor technology it has been possible to fabricate as many as one million transistors on a single 1 cm2 semiconductor chip. A unique property of semiconductors is a remarkable increase in their conductivity with doping. Their response to light and other electromagnetic radiations results in a drastic change in electrical and optical properties, leading to many useful applications as solar cell, photodiode, infrared detectors etc. Therefore, we begin this unit by discussing how to teach the physics of semiconductor devices and their uses. We first describe the basic features of semiconductor materials.
    [Show full text]
  • Analog Electronics What Is This Class All About?
    8/6/2018 Indian Institute of Technology Jodhpur, Year 2018 Analog Electronics (Course Code: EE314) Lecture 1: Introduction & Semiconductor Basics Course Instructor: Shree Prakash Tiwari Email: [email protected] Webpage: http://home.iitj.ac.in/~sptiwari/ Note: The information provided in the slides are taken form text books for microelectronics (including Sedra & Smith, B. Razavi), and various other resources from internet, for teaching/academic use only 1 What is this class all about? • Basic semiconductor device physics and analog integrated circuits. • What will you learn? – Electrical behavior and applications of transistors – Analog integrated circuit analysis and design 1 8/6/2018 Course Description • The first course of electronics “Introduction to Electronics” was to provide an overall flavor of electronics to the 3rd semester students of all the B.Tech. streams. • Next course “Digital Logic and Design” was to provide an overall flavor of Digital Electronics. • Analog Electronics is a course primarily for electrical engineering students to provide an in‐depth understanding of electronic circuit design and analysis. • The primary goal of this course will be to develop an unddderstanding of how electronic circuits work. • Specific topics to be covered include differential and multistage amplifiers, feedback, output stages, a selection of analog integrated circuit topics 3 Books • Razavi, B., Fundamentals of Microelectronics, Wiley India Private Private Ltd. , 2013, 2nd Edition • Gayakwad, R. A., Op‐Amps and Linear Integrated Circuits,
    [Show full text]
  • A Semiconductor
    UNIT IV- ENGINEERING MATERIALS-II Q1. What is a semiconductor? What are intrinsic and extrinsic semiconductors? A semiconductor is a substance, usually a solid chemical element or compound that can conduct electricity under some conditions but not others, making it a good medium for the control of electrical current. It has almost filled valence band, empty conduction band and very narrow energy gap i.e., of the order of 1 eV. Energy gap of Silicon (Si) and Germanium (Ge) are 1.0 and 0.7 eV respectively. Consequently Si and Ge are semiconductors. Effect of temperature on conductivity of semiconductors: At 0 K, all semiconductors are insulators. At finite temperature, the electrical conductivity of a semiconductor material increases with increasing temperature. With increase in temperature, outermost electrons acquire energy and hence by acquiring energy, the outermost electrons leave the shell of the atom. Hence with increase in temperature, number of carriers in the semiconductor material increases and which leads to increase in conductivity of the material. Types of semiconductors: Intrinsic Semiconductor: An intrinsic semiconductor material is chemically very pure and possesses poor conductivity. It has equal numbers of negative carriers (electrons) and positive carriers (holes). A silicon crystal is different from an insulator because at any temperature above absolute zero temperature, there is a finite probability that an electron in the lattice will be knocked loose from its position, leaving behind an electron deficiency called a "hole". This hole can travel from one atom to the adjacent atom by accepting an electron from later one. This process involves formation of new covalent bond and breaking an existing bond by filling up the hole and creating a new hole.in this way, the holes travel fromone atom to the adjacent atoms in crystal lattice.
    [Show full text]