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연습문제풀이

반도체물리 수업 연습문제1.1Calculate the volume per atom and the free-electron Fermi energy EF for lithium, sodium, and potassium, and then evaluate the density of states for each crystal at energy E=EF→ Answer명칭화학명칭a (Å)r (a0)EF(eV)ρ(EF)Lithium리튬 : Li3.493.254.742.2/10Sodium나트륨 : Na4.233.933.241.8/10Potassium칼륨 : K5.234.862.121.5/10ρ(EF) =number of states/a30 eVρ(EF) ==, (여기서 n은 전자밀도이다.)Bohr radius의 값은 a0=0.529X10-8cm이고, 원자당 부피는 4пr3/3 이다.위의 식을 인용하여 풀면,가 되므로이다.이에따라 전자밀도 값을 알수있다.1.2Find an expression for the density of states of a two-dimensional metal.→ Answer :,,1.3What is the crystalline structure (e.g. BCC,FCC,etc.) of NaCl, Si, GaAs, and Na. what is the number of nearest-neighbour atoms in these crystals? What is the lattice constant and the nearest-neighbour separation (in angstroms)?→ Answer :명칭구조No. neighbours atomsa (Å)nearest-neighbour distance(Å)NaClFCC65.642.82Sidiamond45.432.35GaAszinc-blende45.662.45NaBCC84.233.661.4Use the procedure adopted in Problem 1.1 to calculate EF in electroarly-free-electron gap is 0.032eV. What is the magnitude of?→ Answer→→가 된다.2.5Consider a simple cubic lattice in which the atomic separation is 2Å.Determine the electron density from the condition that, whereis the volume of the first Brillouin zone.→ Answer,2.6 Consider the result of Problem 2.4 and determine at what range of wavelengths this crystal is transparent. What would the value ofhave to be for the crystal to be transparent to red light?→ Answer이상일 경우 Red light 발생함.반도체물리 수업 3장 연습문제3.1Find the expression for the group velocity of an electron in a narrow tight- binding band and compare the result with that for a free-electron metal and a nearly-free-electron insulator.* 문제풀이를 위한 기본 식 정리(3-10)eqn(3-12)정리하면at n=l simplifing eqn(3-10)→ Answerin a matal이 된다.3.2Find the effective mass of an electron in a tight-binding band as a function of the atomoic separation a.→ Answer이 된다.3.3Extend the result in eqn(3.15) to the case of a three-dimensional simple cubic lattice.→ Answerat eqn(3.containing 1016 donors per cm3 with binding energy ?E1 < kbT. Estimate the Fermi energy of this system.→ Answer⇒All donors are ionized, hence n=Nd .Since the intrinsic concentration iswe have n >>niFrom eqn(4.6)The factor 6 arises because there are six equivalent conduction band minima (Chapter 5, Table 4.1). Substitude for Nd, m, kT, E and take logarthm to evaluate Eg-Ef=0.21eV. The Fermi energy theregore lies 0.21eV above the conduction band edge.4.3 consider a vibration one-dimensional lattice of atoms A and B show in Fig.4.4a. Use Hooke's law (displacement is proportional to applied force, with proportionality constant α) and carry out a classical equation of motion calculation to generate the normal mode dispersion curves that are shown in Fig.4.4b.→ Answer⇒force on atom M, proportional to displacement u, 2n+1 atom4.4show that the absorption spectrum of a nearly-free-electron insulator is characterized by strong peaks at photon energies corresponding to direct (vertical) transitiohat a uniform gradient of electron concentration is formed from zero to Ne=1014cm-3. Determine what electric field must be applied to generate a drift electron current that is exactly equal to the diffusion current density ( T=300K ).→ Answer4.9Compare electron conductivity in a simple metal and in a semiconductor at room temperature. Assume that the relaxation times and m* are the same in both materials.→ Answer4.10 A sample of silicon crystal is illuminated with light of wavelength λ at T=300K. What is the threshold value of λ n angstroms at which electron-hole pairs are created? If the carrier lifetime in this sample is 1 ㎲, how long will it take for the electron pair concentraion to be reduced by 90%.→ Answer반도체물리 수업 5장 연습문제5.1Examine the position of atoms in the unit cube of FIg. 5.2.(a) Use Table 5.1 to calculate the next-nearest distance between atoms in terms of the lattice constant a and compare it with the distance between nearest neighbours.→ Answerdistance nearest neighbourtant and the observed and calculated forbidden gaps in materials consisting of atoms from the same row of the Periodic Table. List these materials in the order of increasing ionicity. Explain the result in simple qualitative terms.→ AnswerGaAs is more ionic than Ge and ZnSe is more ionic than GaAs5.5 The density of electron states was defined as the number of states in a unit energy interval. Inspect visually the band structures in Fig. 5.3 to identify the transition energies (gaps) at which a large density of states should occur. How does this affect optical properties of these material?→ AnswerThe conduction band minima near the X and Γ points. The optical transitions across the 9vertical) gap at these points will be strong5.6Find a compound semiconductor or a semiconductor alloy such that the material is likely to be an efficient absorber of visible light in the res region of the spectrum.→ AnswerThe fundamental gap is hc/λ; λ?6200A gives an energy of about 2eV.We need, for instancetion

공학/기술| 2010.05.11| 13페이지| 1,000원| 조회(187)

물리, Physics, semiconductor, microstructures, 반도체물리

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spin 소자

* 전자의 스핀현상 연구Discovery of electronsJ.J. Thomson (1897) Spin-dependent electron scatteringN.F.Mott (1936) TransistorBell Laboratory (1948) Giant magnetoresistance(GMR)Baibichet al (1988) Tunneling magnetoresistance(TMR)Moodera(1995) 1600년William Gilbert : 지구는 하나의 거대한 자석 조그만 자석들의 방향은 구형 자석의 자기자오면(magnetic merdian)의 방향과 일치5Photonic & Electronic Thin film Lab 1920년경 전자도 스핀을 가짐 → 전자 스핀 자기 양자수로 표시

공학/기술| 2010.05.11| 20페이지| 1,500원| 조회(152)

반도체, 자성체, 스핀, spin, 전자스핀, 스핀소자

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Electron transport in microstructures

1. Velocity overshoot in hot-electron transport2. Transfer of hot electrons into secondary valleys3. Impact ionization4. Breakdown voltage5. Poole-Frenkel effect6. Mobility enhancement in modulation-doped structure7. Superconductivity8. Josephson tunnelling

공학/기술| 2010.05.11| 17페이지| 1,500원| 조회(205)

Electron transport, microstructures, 전자이동, Breakdown voltage

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Thin –Film Evaporation Processes

1 Introduce to 1. Introduction Evaporation: 액체 표면으로부터 원자와 분자가끓는점 미만에서 기화하는 현상 Vacuum Evaporation: 진공으로 된 용기 내 증착하고자하는 물질에 열을 가해서 고체 또는액체로부터 증기를 발생시켜 발생된증기를 기판에 증착 시키는 과정(고진공, 직진성을 가짐)• 기판과 소스 거리 : 10~100cm 이내• 증기용기 내 압력 : 10-5 Torr 이하로 유지 종류 : Thermal evaporation, e-beam evaporation 등 장점 : 공정이 단순, 증착률이 높으며 속도가 빠름장치 구성이 간단 (가격 저렴)다양한 물질에 대해 쉽고 빠르게 성장가능고융점 재료 증착가능 단점 : 장비 크기가 제한됨공정 중 불순물 혼입가능, 기판 클리닝 불가능film quality가 나쁨(표면굴곡 발생)박막과 기판사이 밀착강도 약함

공학/기술| 2010.05.11| 22페이지| 1,500원| 조회(329)

진공, 박막, thin film, Evaporation, purity, film ..

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