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Importance of English in Optoelectronic Devices Study

Learn the crucial role of English in studying optoelectronic devices and semiconductors, band structure, atomic arrangement, and crystal growth. Explore how mastering English can open up career opportunities in this field.

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Importance of English in Optoelectronic Devices Study

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  1. Why English is Important • English ability would save life • English ability gives you opportunities http://www.youtube.com/watch?v=tcseWVNmda8 e.g. Job opening in TSMC http://www.tsmc.com/chinese/careers/jobs.html http://www.youtube.com/watch?v=GT86iWiH2mI

  2. What should you do to learn English in this class? • Read largely - preview textbook before class - review textbook and note after class • Increase your vocabulary • Invest your time to learn English regularly - Reading CNN, yahoo, newspaper - Listening radio youtube watching TV

  3. Ch.1 Introduction • Optoelectronic devices: • - devices deal with interaction of electronic and optical processes • Solid-state physics: • - study of solids, through methods such as quantum mechanics, crystallography, electromagnetism and metallurgy • Elemental semiconductors: • - Si, Ge, ..etc. • - indirect bandgap, low electric-optics conversion efficiency • Compound semiconductors • -III-V (e.g. GaN, GaAs), II-VI • -direct bandgap, high electric-optics conversion efficiency • GaAs, InP • - higher mobility than Si, Ge, • - energy band gap, Eg: 1.43 (GaAs), 1.35 (InP) • - most common substrate, used to grow up compound semiconductors

  4. Periodic Table

  5. Band structure • Band structure: • - results of crystal potential that originates from equilibrium arrangement of atoms • in lattice - directed from potential model and electron wave equation (Schrodinger equation) time-dependent Schrodinger equation E: electron energy, φ:wave equation, m: electron mass, ħ: Plank constant

  6. Electron energy band diagram v.s. wave number

  7. Energy bandgap v.s. lattice constant

  8. Wavelength (Bandgap) Engineering Reference article: http://www.tf.uni-kiel.de/matwis/amat/semi_en/kap_5/backbone/r5_1_4.html

  9. Energy bandgap v.s. lattice constant • Constrains for forming compound semiconductors: • (1) requirement of lattice match, (2) availability of suitable substrates • GaAs and InP are most common substrates used to grow up compound semiconductors • (Note: InAs, InSb and GaSb substrates are availabe, but not as readily as GaAs and InP, • moreover, all the ternary and quaternary alloys of interest are mis-matched to these substrates) • only InxGa1-xAs and InxAl1-xAs lattice-matched on InP substrate • all AlxGa1-xAs can lattice-match on GaAs substrate

  10. Bonding in solids • Van der Waals bonding: attractions between atoms, molecules, and surfaces. e.g.: inert gas (like Ar), the ability of gecko to hang on a glass surface • Ionic bonding: electron exchange between atoms produces positive and negative ions which attract each other by Coulomb-type interactions e.g. NaCl, KCl • covalent bonding sharing of electrons between neighboring atoms e.g.: elemental and compound semiconductors • Metallic bonding: valence electrons are shared by many atoms (bonding not directional, electron free or nearly free contributed to conductivity) e.g.: Zn

  11. Body-Centered Cubic (BCC) structure http://stokes.byu.edu/bcc.htm e.g. iron, chromium, tungsten, niobium

  12. Face-Centered Cubic (FCC) structure e.g.: aluminum, copper, gold, silver http://stokes.byu.edu/fcc.htm

  13. Diamond Cubic (FCC) structure http://zh.wikipedia.org/zh-tw/File:Diamond_Cubic-F_lattice_animation.gif

  14. Diamond structure v.s. Zincblende structure • Diamond structure, Zincblende structure e.g.: Si, Ge e.g.: GaAs, and some many binary compound semiconductors

  15. Atomic arrangement in different solids

  16. Dislocation & strain • Dislocationoccurs if - epitaxial layer thickness > hc (critical thickness), or - epitaxial layer thickness < hc, but with large mismatch • Strain occurs if - epitaxial layer thickness < hc , and with small mismatch

  17. Strain semiconductor • a) lattice match b) compressive strain c) tensile strain • Strain offers flexibility for restriction of lattice mismatch • Pseudomorphic: thin film take on morphology (lattice • constant) of the substrate

  18. Crystal Growth • Bulk growth: - furnace growth - pulling technique e.g. Czochralski • Epitaxial growth: - Liquid Phase Epitaxy (LPE) - Vapor Phase Epitaxy (VPE), or termed Chemical Vapor Deposition (CVD) - Molecular Beam Epitaxy (MBE)

  19. Epitaxy • epi means “above” taxis means “in order manner” epitaxy can be translated to “to arrange upon” • with controlled thickness and doping • subtract acts as a seed crystal, deposited film takes on a lattice structure and orientation identical to the subtract • different from thin film deposition that deposit polycrystalline or amorphous film • - homoepitaxy: epi and subtract are with the same material • epi layer more pure than subtract and have different doping level - hetroepitaxy: epi and subtract are with different material • Examples includes - Si-based process for BJT and CMOS, or - compound semiconductors, such as GaAs

  20. Epitaxy Material Growth Methods • Liquid Phase Epitaxy • Vapor Phase Epitaxy (VPE), or termed Chemical Vapor Deposition (CVD) - formation of condensed phase from gas of different chemical composition - distinct from physical vapor deposition (PVD) such as sputtering, e-beam deposition, MBE (condensation occurs without chemical change) - gas stream through a reactor and interact on a heated subtract to grow epi layer • Molecular Beam Epitaxy

  21. Doping of Compound Semiconductors • Intrinsic materials:undoped • - Undoped materials by epitaxy technology have more carriers than in intrinsic • material. e.g. GaAs: 1013 /cm3 (instrinsic carrier concentration: 1.8x106 /cm3) • - impurity comes from source materials, carrier gases, process equipment, or • subtract handle • Extrinsic materials: • - n-type: III sub-lattice of III-V compound is substituted by IV elements: impurity terms “donor” • - p-type: V sub-lattice of III-V compound is substituted by IV elements: impurity terms “acceptor” http://www.siliconfareast.com/sigegaas.htm

  22. Optical fiber • Silica optical fibers have a lowest loss at 1.55 um, and a lowest dispersion at 1.3 um • In0.53Ga0.47As (Eg=0.47ev)/In0.52Al0.48As (Eg=1.45ev) heterojunction on InP can be used for optical fiber because Eg of InGaAs is close to 1.55 and 1.3 um • Note: Why GaAs/AlGaAs can’t be used here?

  23. Energy band theory

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