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課程講義 光電元件物理 南台科技大學光電系 吳坤憲 1 Physics of Optoelectronic Devices Part I. Introduction to Physics of Semiconductor Devices Part II. Basic Concepts of Optoelectronic Devices Part III. Light Emitting Diodes (LEDs) Part IV. Semiconductor Laser Diodes Part V. Photodetectors and Solar Cells Part VI. Fabrication Technology 2 I. Introduction to Physics of Semiconductor Devices 半導體材料 Solid-State Materials Semiconductor Materials Basic Crystal Structure Energy-band Diagram Intrinsic and Extrinsic 半導體元件 (Devices) Junctions Carrier Transport The P-N Diode BJT and MOSFET 3 5W for Semiconductors What? 導電度界於導体與絕緣體之間的材料 Why? 半導體為現代電子工業的核心 Where? 應用於幾乎所有的電子產品(元件) When? 1988年起電子工業成為世界上最大規模的工業 How? 導電性可控制 4 Solid-State Materials • Conductor – Mn: ~ 105 – Cu: ~ 8 × 106 – Fe: ~ 107 • Semiconductor – Si: ~ 105 – doped-Si: 105 ~ 10-5 • Insulator – Quartz: ~ 10-18 – Plastics: ~10-13 – GaAs: ~ 10-6 Resitivity (-cm) Conductivity (-cm)-1 5 Portion of the Periodic Table related to semiconductors 6 Element and Compound Semiconductors Element semiconductors Si, Ge, C (diamond).. , etc.. Compound Semiconductors – III-V compound semiconductors • Binary: GaAs, InP, GaP, GaN, AlAs, InAs… • Ternary: Al1-xGaxAs, GaAsxP1-x , InxGa1-xAs • Quaternary: InxGa1-xAsyP1-y – II-VI compound semiconductors • CdS, CdSe, CdTe, ZnS, ZnSe, ZnTe, ZnO, HgCdTe, etc.. – IV-IV compound semiconductors • SiC, SiGe – IV-VI compound semiconductors • PbS, PbTe 7 Various Semiconductor Materials 8 改變半導體導電性的主要方法 溫度 (Temperature) – Thermal sensors 照光 (Illumination) – optoelectronic devices : Photodetector, Solar Cell….ect.. 摻雜 (Doping) – 大幅增加導電度 – 形成P 型及N型半導體 – 形成P/N接面:多數半導體元件之基本結構 9 Applications of Semiconductors Device 表 1-1 主要的半導體材料及相關的應用領域 種 類 材 料 應 用 積體電路 (Integrated Circuits) Si Si 太陽能電池 (Solar Cell) 微機械元件 (Micromechanics) 化合物 GaAs 高速、高頻積體電路 GaP 發光二極體 (Light Emitted Diode) InP 光測器 (Photo Detector) ZnSe 半導體雷射 (Semiconductor Laser) ZnS 平面顯示器 (Flat Panel Displays) 10 Crystallization of materials 11 Crystal and Lattice Crystal (結晶體) – The semiconductor materials are basically assumed as single crystals to simplify the analysis. Lattice (晶格) – The periodic arrengment of atoms in a crystal Lattice Constant (晶格常數) – The dimension a is called the lattice constant Three cubic-crystal unit cells. (a) Simple cubic. (b) Body-centered cubic (c) Face-centered cubic. 12 The Diamond Structure (a) Diamond lattice. (b) Zincblende lattice. 13 Crystal Plane and Direction A (623)-crystal plane Miller indices of some important planes in a cubic crystal 14 Covalence Bonds A tetrahedron bond (a) 3-D. (b) 2-D 15 Conduction Electron and Hole Formation of intrinsic carriers 16 Donor and Acceptor Formation of extrinsic carriers 17 Energy-Band Diagram Metal Semiconductor Insulator 18 Simplified Energy-Band Diagram 19 Energy-Momentum Band Diagram 20 Band Structures for Si and GaAs Si GaAs 21 Direct and Indirect Bandgap Semiconductors • • Direct transition: band to band photon emission Indirect transition: via defect or impurity-related states phonon emission Direct Bandgap Indirect Bandgap 22 Extrinsic (Doped) Semiconductor Donor Level Acceptor Level 23 Various Impurities 24 Intrinsic, N-type and P-type semiconductors (1) Intrinsic (2) N-type (3) P-type 25 Intrinsic and Extrinsic Silicon Intrinsic Semiconductor (本質半導體) – 導電電子數量與電洞數量大約相同的半導體 – 通常指未經摻雜的半導體(Undoped Semiconductor) N-type Semiconductor (N型半導體) – 多數載子(majority carrier)為電子的半導體 – 矽晶體中摻雜V 族原子則形成N型半導體 P-type Semiconductor (P型半導體) – 多數載子(majority carrier)為電洞的半導體 – 矽晶體中摻雜III族原子則形成P型半導體 26 Impurities for III-V Compound Semiconductors Donor (施體) – Column IV (S, Se,Te, etc.) impurity substitute for column V (As) Acceptor(受體) – Column II (Be, Zn, Cd, etc.) impurity substitute for column III (Ga) Amphoteric impurity (雙性雜質) – substituting Ga for donor (low T) – substituting As for acceptor (high T) 27 Basic Building Blocks of Semiconductor Devices (a) M-S Junction (b) P-N Junction (c) Heterojuction (d) MOS structure 28 Semiconductor Devices • Bipolar Devices – – – – • Unipolar Devices – – – – – • P-N Junction Diode Bipolar Junction Transistor (BJT) Heterojunction Bipolar Transistor (HBT) Thyristor and related power devices Junction Field Effect Transistor (JFET) Metal-Oxide-Semiconductor FET (MOSFET) MOS Diode (Capacitor) Complementary MOS (CMOS) BiMOS and BiCMOS Power MOS High-Speed Devices – – Metal-Semiconductor FET (MESFET) Modulation-Doped FET (MODFET), High-Electron-Mobility Transistor (HEMT) 29 Semiconductor Devices (continued) • Microwave Devices – – – – – • Tunnel diode IMPATT diode Transferred-Electron Device (TED) Quantum-Effect Devices Hot-Electron Devices Photonic Devices – – – Light Emitting Diode (LED) Semiconductor Laser (Laser Diode, LD) Photodetector • • – – Photodiode (PD), Avalanche Photodiode (APD) Phototransistor (PT) Solar Cell Display Devices • • Thin-Film Transistor LCD (TFT-LCD) Organic Electroluminescence Display (OELD) or Organic Light Emitting Diode (OLED) 30 Semiconductor Devices (continued) • Integrated Devices – Passive Components • IC Resistor, IC Capacitor, IC Inductor – MOS Menory • • • • • • • Dynamic Random Access Memory (DRAM) Static Random Access Memory (SRAM) Nonvolatile Memory Erasable-Programmable Read-Only Memory (EPROM) Electrically Erasable-Programmable Read-Only Memory (EEPROM) Flash Memory Single-Electron Memory 31 Carrier Drift Carrier Drift (飄移) – Carrier transport in an applied electric field – vn = -nE – vp = pE – n (p): carrier mobility (移動率) (cm2/V-s) – Drift Current Density J = (qnn + qpp)E 32 Mobility and Resistivity (Conductivity) -1 = L-1 + I-1 = -1 = [q(n n + pp)]-1 33 Carrier Diffusion Carrier Diffusion (擴散) – The carriers tend to move from a region of high concentration to a region of low concentration. – Diffusion Current Density Jn = qDn (dn/dx) Dn: diffusivity (diffusion coefficient) Einstein relation: Dn = ( kT/q)n) 34 Current Density Equations • Jn = qnnE + qDn (dn/dx) • Jp = qppE - qDp (dp/dx) • J = J n + Jp 35 Carrier Generation and Recombination Direct generation and recombination of electron-hole pairs: (a) at thermal equilibrium. (b) under illumination Decay of photoexcited carriers 36 Indirect Generation-Recombination Process Indirect G-R process at thermal equilibrium 37 The P-N Diode --- Under Thermal Equlibrium P-type and N-type semiconductors before and after the junction formed A p-n junction with abrupt doping charges at the metallurgical junction 38 The P-N Diode --- Under Biasing Conditions Current-voltage characteristics of a typical Si p-n junction (a) Thermal equilibrium (b) Forward-bias condition. (c) Reverse-bias condition 39 The P-N-P Transistor 40 The MOSFET 41 The CMOS 42 The Thin-Film Transistor 43