President UniversityErwin SitompulSDP 1/1 Dr.-Ing. Erwin Sitompul President University Lecture 1 Semiconductor Device Physics

President UniversityErwin SitompulSDP 1/2 Textbook: “Semiconductor Device Fundamentals”, Robert F. Pierret, International Edition, Addison Wesley, Textbook and Syllabus Syllabus: Chapter 1: Semiconductors: A General Introduction Chapter 2: Carrier Modeling Chapter 3: Carrier Action Chapter 5: pn Junction Electrostatics Chapter 6: pn Junction Diode: I–V Characteristics Chapter 7:pn Junction Diode: Small-Signal Admittance Chapter 8:pn Junction Diode: Transient Response Chapter 14:MS Contacts and Schottky Diodes Chapter 9: Optoelectronic Diodes Chapter 10:BJT Fundamentals Chapter 11: BJT Static Characteristics Chapter 12:BJT Dynamic Response Modeling Semiconductor Device Physics

President UniversityErwin SitompulSDP 1/3 Grade Policy Final Grade =10% Homework + 20% Quizzes + 30% Midterm Exam + 40% Final Exam + Extra Points  Homeworks will be given in fairly regular basis. The average of homework grades contributes 10% of final grade.  Homeworks are to be written on A4 papers, otherwise they will not be graded.  Homeworks must be submitted on time, one day before the schedule of the lecture. Late submission will be penalized by point deduction of –10·n, where n is the total number of lateness made.  There will be 3 quizzes. Only the best 2 will be counted. The average of quiz grades contributes 20% of final grade. Semiconductor Device Physics  The maximum lateness in coming to class is 25 minutes, otherwise attendance will not be counted.

President UniversityErwin SitompulSDP 1/4  Midterm and final exams follow the schedule released by AAB (Academic Administration Bureau).  Make up of quizzes must be held within one week after the schedule of the respective quiz.  Make up for mid exam and final exam must be requested directly to AAB. Semiconductor Device Physics Grade Policy Heading of Homework Papers (Required) Semiconductor Device Physics Homework 2 Ito Chen March 2021 D6.2. Answer:

President UniversityErwin SitompulSDP 1/5 Grade Policy  In order to maintain the integrity, the score of a make up quiz or exam can be multiplied by 0.9 (i.e., the maximum score for a make up will be 90).  Extra points will be given every time you solve a problem in front of the class or answer a question. You will earn 1 or 2 points.  Lecture slides can be copied during class session. The updated version will be available on the lecture homepage around 1 day after class schedule. Please check regularly.  The use of internet for any purpose during class sessions is strictly forbidden.  You are expected to write a note along the lectures to record your own conclusions or materials which are not covered by the lecture slides. Semiconductor Device Physics

President UniversityErwin SitompulSDP 1/6 Greek Alphabet —pie —fie —k-eye —sigh —zz-eye —taw —new —mew Semiconductor Device Physics

President UniversityErwin SitompulSDP 1/7 Chapter 1 Semiconductors: A General Introduction Semiconductor Device Physics

President UniversityErwin SitompulSDP 1/8 Chapter 1Semiconductors: A General Introduction What is a Semiconductor? Low resistivity  “conductor” High resistivity  “insulator” Intermediate resistivity  “semiconductor” The conductivity (and at the same time the resistivity) of semiconductors lie between that of conductors and insulators.

President UniversityErwin SitompulSDP 1/9 No recognizable long-range order Completely ordered in segments Entire solid is made up of atoms in an orderly three- dimensional array Chapter 1Semiconductors: A General Introduction What is a Semiconductor? Semiconductors are some of the purest solid materials in existence, because any trace of impurity atoms called “dopants” can change the electrical properties of semiconductors drastically. Unintentional impurity level: 1 impurity atom per 10 9 semiconductor atom. Intentional impurity ranging from 1 per 10 8 to 1 per Most devices fabricated today employ crystalline semiconductors. polycrystallineamorphous crystalline

President UniversityErwin SitompulSDP 1/10 Semiconductor Materials Elemental: Si, Ge, C Compound:IV-IVSiC III-VGaAs, GaN II-VICdSe Alloy:Si 1-x Ge x Al x Ga 1-x As Chapter 1Semiconductors: A General Introduction As: Arsenic Cd: Cadmium Se: Selenium Ga: Gallium

President UniversityErwin SitompulSDP 1/11 From Hydrogen to Silicon Chapter 1Semiconductors: A General Introduction

President UniversityErwin SitompulSDP 1/12 The Silicon Atom Chapter 1Semiconductors: A General Introduction 14 electrons occupying the first 3 energy levels: 1s, 2s, 2p orbitals are filled by 10 electrons. 3s, 3p orbitals filled by 4 electrons. To minimize the overall energy, the 3s and 3p orbitals hybridize to form four tetrahedral 3sp orbital. Each has one electron and is capable of forming a bond with a neighboring atom.

President UniversityErwin SitompulSDP 1/13 The Si Crystal “Diamond Lattice” a Chapter 1Semiconductors: A General Introduction Each Si atom has 4 nearest neighbors. Atom lattice constant (length of the unit cell side) a = 5.431A, 1A = 10 –10 m °° Each cell contains: 8 corner atoms 6 face atoms 4 interior atoms

President UniversityErwin SitompulSDP 1/14 How Many Silicon Atoms per cm –3 ? Chapter 1Semiconductors: A General Introduction Number of atoms in a unit cell: 4 atoms completely inside cell Each of the 8 atoms on corners are shared among 8 cells  count as 1 atom inside cell Each of the 6 atoms on the faces are shared among 2 cells  count as 3 atoms inside cell  Total number inside the cell = = 8 Cell volume = (.543 nm) 3 = 1.6 x 10 –22 cm 3 Density of silicon atom = (8 atoms) / (cell volume) = 5 × atoms/cm 3 What is density of silicon in g/cm 3 ?

President UniversityErwin SitompulSDP 1/15 Compound Semiconductors Chapter 1Semiconductors: A General Introduction “Zincblende” structure III-V compound semiconductors: GaAs, GaP, GaN, etc.

President UniversityErwin SitompulSDP 1/16 Crystallographic Notation NotationInterpretation ( h k l ) crystal plane { h k l } equivalent planes [ h k l ] crystal direction equivalent directions h: inverse x-intercept of plane k: inverse y-intercept of plane l: inverse z-intercept of plane (h, k and l are reduced to 3 integers having the same ratio.) Miller Indices Chapter 1Semiconductors: A General Introduction

President UniversityErwin SitompulSDP 1/17 Crystallographic Planes (632) plane(001) plane(221) plane Chapter 1Semiconductors: A General Introduction _

President UniversityErwin SitompulSDP 1/18 Crystallographic Planes Chapter 1Semiconductors: A General Introduction

President UniversityErwin SitompulSDP 1/19 Crystallographic Planes of Si Wafers Chapter 1Semiconductors: A General Introduction Silicon wafers are usually cut along a {100} plane with a flat or notch to orient the wafer during integrated-circuit fabrication. The facing surface is polished and etched yielding mirror-like finish.

President UniversityErwin SitompulSDP 1/20 Crystal Growth Until Device Fabrication Chapter 1Semiconductors: A General Introduction

President UniversityErwin SitompulSDP 1/21 Unit cell: View in direction Crystallographic Planes of Si View in direction Chapter 1Semiconductors: A General Introduction View in direction

President UniversityErwin SitompulSDP 1/22 Chapter 2 Carrier Modeling

President UniversityErwin SitompulSDP 1/23 Chapter 2Carrier Modeling Electronic Properties of Si Silicon is a semiconductor material. Pure Si has a relatively high electrical resistivity at room temperature. There are 2 types of mobile charge-carriers in Si: Conduction electrons are negatively charged, e = –1.602  10 –19 C Holes are positively charged, p =  10 –19 C The concentration (number of atom/cm 3 ) of conduction electrons & holes in a semiconductor can be influenced in several ways: Adding special impurity atoms (dopants) Applying an electric field Changing the temperature Irradiation

President UniversityErwin SitompulSDP 1/24 Hole Conduction electron Chapter 2Carrier Modeling Bond Model of Electrons and Holes When an electron breaks loose and becomes a conduction electron, then a hole is created. 2-D Representation

President UniversityErwin SitompulSDP 1/25 Chapter 2Carrier Modeling What is a Hole? A hole is a positive charge associated with a half-filled covalent bond. A hole is treated as a positively charged mobile particle in the semiconductor.

President UniversityErwin SitompulSDP 1/26 Chapter 2Carrier Modeling Conduction Electron and Hole of Pure Si n i = intrinsic carrier concentration n i ≈ cm –3 at room temperature Covalent (shared e – ) bonds exists between Si atoms in a crystal. Since the e – are loosely bound, some will be free at any T, creating hole-electron pairs.

President UniversityErwin SitompulSDP 1/27 Energy states (in Si atom) Chapter 2Carrier Modeling Si: From Atom to Crystal The highest mostly-filled band is the valence band. The lowest mostly-empty band is the conduction band. Energy bands (in Si crystal)

President UniversityErwin SitompulSDP 1/28 EcEc EvEv Electron energy For Silicon at 300 K, E G = 1.12 eV 1 eV = 1.6 x 10 –19 J E G, band gap energy Chapter 2Carrier Modeling Energy Band Diagram Simplified version of energy band model, indicating: Lowest possible conduction band energy (E c ) Highest possible valence band energy (E v ) E c and E v are separated by the band gap energy E G.

President UniversityErwin SitompulSDP 1/29 Band gap energies Chapter 2Carrier Modeling Measuring Band Gap Energy E G can be determined from the minimum energy (h ) of photons that can be absorbed by the semiconductor. This amount of energy equals the energy required to move a single electron from valence band to conduction band. Photon photon energy: h  = E G EcEc EvEv Electron Hole

President UniversityErwin SitompulSDP 1/30 Carriers Chapter 2Carrier Modeling Completely filled or empty bands do not allow current flow, because no carriers available. Broken covalent bonds produce carriers (electrons and holes) and make current flow possible. The excited electron moves from valence band to conduction band. Conduction band is not completely empty anymore. Valence band is not completely filled anymore.

President UniversityErwin SitompulSDP 1/31 Band Gap and Material Classification E c E v E G = 1.12 eV Si Metal E v E c E E c v E c E G = ~8 eV SiO 2 E v Chapter 2Carrier Modeling Insulators have large band gap E G. Semiconductors have relatively small band gap E G. Metals have very narrow band gap E G. Even, in some cases conduction band is partially filled, E v > E c.

President UniversityErwin SitompulSDP 1/32 Carrier Numbers in Intrinsic Material Chapter 2Carrier Modeling More new notations are presented now: n : number of electrons/cm 3 p : number of holes/cm 3 n i : intrinsic carrier concentration In a pure semiconductor, n = p = n i. At room temperature, n i = 2  10 6 /cm 3 in GaAs n i = 1  /cm 3 in Si n i = 2  /cm 3 in Ge

President UniversityErwin SitompulSDP 1/33 Semester Schedule Semiconductor Device Physics FCS 1SDP 1 SDP 2 FCS 2 Rec 1

President UniversityErwin SitompulSDP 1/34 Semester Schedule Semiconductor Device Physics SDP 3FCS 3 Rec 2 SDP 4 FCS 4 FCS 5 FCS 6 Mid Rec 3 Rec 4 SDP 5 SDP 6 Rec 5

President UniversityErwin SitompulSDP 1/35 Semester Schedule Semiconductor Device Physics SDP 8 Mid FCS 7 FCS 8 FCS 9 FCS 10 ? Rec 5 Rec 6 Rec 7 Rec 8 SDP 7 SDP 9

President UniversityErwin SitompulSDP 1/36 Semester Schedule Semiconductor Device Physics Final FCS 11 FCS 12 Rec 9 Rec 10 SDP 10 SDP 11