Semiconductors for Optoelectronics: Basics and Applications

Description

This book provides in-depth knowledge about the fundamental physical properties of bulk and low dimensional semiconductors (LDS). It  also explains their applications to optoelectronic devices. The book incorporates two major themes. The first theme, starts from the fundamental principles governing the classification of solids according to their electronic properties and leads to a detailed analysis of electronic band structure and electronic transport in solids. It then focuses on the electronic transport and optical properties of semiconductor compounds, size quantization and the analysis of abrupt p-n junctions where a full analysis of the fundamental properties of intrinsic and doped semiconductors is given. The second theme is device-oriented. It  aims to provide the reader with understanding of the design, fabrication and operation of optoelectronic devices based on novel semiconductor materials, such as high-speed photo detectors, light emitting diodes, multi-mode and single-mode lasers and high efficiency solar cells. The book appeals to researchers and high-level undergraduate students. Preface Contents 1 Electrical Properties of Solids 1.1 Ohm’s Law and Ohmic Conduction 1.2 Resistance and Resistivity 1.3 Conductance and Conductivity 1.4 Classification of Solids 1.4.1 Metals, Semiconductors and Insulators 1.4.2 Electrical Conductivity, Charge Carrier Density and Carrier Mobility 1.4.3 Bandstructure of Solids 1.4.4 Electron Distribution Within Energy Bands at T0 K 1.4.5 Valence Band, Conduction Band and Electron Delocalisation 1.4.6 Electrical Conductivity of Solids at T0 K 1.4.7 Electrical Conductivity of Solids at Finite Temperatures 1.4.8 Free Charge Carriers in Semiconductors 1.4.9 Electrons and Holes 1.4.10 Bipolar Conductivity 1.5 Bandstructure of Various Semiconductors References 2 Intrinsic and Extrinsic Semiconductors 2.1 Density of States Function 2.2 Fermi–Dirac Distribution Function 2.2.1 Electron Distribution at Absolute Zero Temperature 2.2.2 Distribution of Electrons at Finite Temperatures 2.2.3 Charge Neutrality Condition 2.3 Intrinsic Semiconductors 2.3.1 Free Carrier Densities in Intrinsic Semiconductors 2.3.2 Temperature Dependence of Carrier Densities 2.3.3 Conductivity 2.4 Extrinsic Semiconductors 2.4.1 n- and p-Type Semiconductors 2.4.2 n-Type and p-Type Doping 2.4.3 Binding Energy of Hydrogenic Impurities 2.4.4 The Fermi Level in Extrinsic Semiconductors 2.4.5 Carrier Compensation 2.5 Temperature Dependence of Carrier Density in Extrinsic Semiconductors Suggested Reading List 3 Charge Transport in Solids 3.1 Transport in an Electric Field 3.1.1 Particle Current and Charge Current 3.1.2 Drift Velocity and Carrier Mobility 3.1.3 Matthiessen’s Rule and the Total Mobility 3.1.4 Temperature Dependence of Mobility 3.1.5 Electric Field Dependence of Mobility 3.1.6 Conductivity 3.1.7 Current Density 3.1.8 Bipolar Conductivity 3.2 Diffusion Conductivity 3.2.1 Fick’s Law 3.2.2 Diffusion Current Density 3.2.3 Drift and Diffusion Current Densities 3.2.4 Hall Effect 3.3 Non-equilibrium Carriers in Semiconductors 3.3.1 Semiconductor in Thermal Equilibrium 3.3.2 Generation and Recombination of Excess Carriers 3.3.3 Continuity Equations 3.3.4 Ambipolar Transport 3.3.5 Photoconductivity 3.4 Quasi-Fermi Levels 3.5 Excess Carrier Lifetime 3.5.1 Shockley–Read–Hall Recombination Theory 3.5.2 Low Injection Limit References 4 The p-n Junction Diode 4.1 p-n Junction in Equilibrium 4.1.1 Built-In Potential 4.1.2 Depletion Layer Width and the Built-In Electric Field 4.2 p-n Junction Under an External Electric Field 4.2.1 Charge Injection and Current in p-n Junction 4.2.2 Minority and Majority Carriers in a p-n Junction 4.3 High Voltage Effects 4.3.1 Forward Bias: High Injection Region 4.3.2 Reverse Bias: Impact Ionisation 4.4 Junction Capacitance 4.5 Temperature Dependence of Diode Current 4.6 Tunnel Diode Suggested Reading List 5 Solar Cells (Photovoltaic Cells) 5.1 Principles of Solar Cells 5.1.1 Solar Radiation 5.1.2 Material Choice for Solar Cells 5.1.3 p-n Junction Under Illumination 5.1.4 Solar Cell Parameters 5.2 Design Considerations 5.2.1 Principal Considerations for Solar Cell Design 5.2.2 Enhancement of Efficiency 5.3 Advantages and Disadvantages of Solar Cells 5.4 Thermophotovoltaic (TPV) Cells 5.4.1 Advantages and Disadvantages of TPV Cells Reference 6 Photodetectors 6.1 Optical Transitions in Direct Bandgap Semiconductors 6.2 Choice of Material and Wavelength of Operation 6.3 Operating Temperature 6.4 pinPhotodiode 6.5 Quantum Efficiency and Response 6.6 Rise Time and Bandwidth 6.7 Avalanche Photodiodes References 7 Light Emitting Diodes and Semiconductor Lasers 7.1 Definitions 7.1.1 Absorption and Emission Rates: Einstein Relations 7.1.2 Population Inversion 7.1.3 Optical Feedback and Laser Oscillations 7.1.4 Threshold Condition for Laser Oscillations 7.2 Optical Processes in Semiconductors 7.3 Light Emitted Diodes (LEDs) 7.4 Semiconductor Lasers 7.4.1 Homojunction Lasers 7.4.2 Efficiency of a Semiconductor Laser 7.4.3 Gain and Threshold Current 7.4.4 Temperature Dependence of Threshold Current 7.5 Heterojunction Lasers 7.6 Quantum Well Lasers 7.6.1 Low Dimensional Semiconductors: Quantum Wells 7.6.2 Density of States in 2D 7.6.3 Absorption in Quantum Well Systems 7.6.4 Quantum Well Lasers 7.7 Vertical Cavity Surface Emitting Laser—VCSEL 7.7.1 Temperature Dependence of VCSELs 7.8 Distributed Feedback Lasers (DFB) References Solution for Selected Problems Index