Nitride Semiconductors and Devices

This timely monograph addresses an important class of semiconductors and devices that constitute the underlying technology for blue lasers. It succinctly treats structural, electrical and optical properties of nitrides and the substrates on which they are deposited, band structures of nitrides, optical processes, deposition and fabrication technologies, light-emitting diodes, and lasers. It also includes many tables and figures detailing the properties and performance of nitride semiconductors and devices.

Contenu

1. Introduction.- 2. General Properties of Nitrides.- 2.1 Crystal Structure of Nitrides.- 2.2 Gallium Nitride.- 2.2.1 Chemical Properties of GaN.- 2.2.2 Thermal and Mechanical Properties of GaN.- 2.3 Aluminum Nitride.- 2.3.1 Thermal and Chemical Properties of AlN.- 2.3.2 Mechanical Properties of AlN..- 2.3.3 Electrical Properties of AlN.- 2.3.4 Optical Properties of AlN.- 2.4 Indium Nitride.- 2.4.1 Crystal Structure of InN.- 2.4.2 Mechanical and Thermal Properties of InN.- 2.4.3 Electrical Properties of InN.- 2.4.4 Optical Properties of InN.- 2.5 Ternary and Quaternary Alloys.- 2.5.1 AlGaN Alloy.- 2.5.2 InGaN Alloy.- 2.5.3 InAIN Alloy.- 2.6 Substrates for Nitride Epitaxy.- 2A Appendix: Fundamental Data for Nitride Systems.- 3. Electronic Band Structure of Bulk and QW Nitrides.- 3.1 Band-Structure Calculations.- 3.2 Effect of Strain on the Band Structure of GaN.- 3.3 k·p Theory and the Quasi-Cubic Model.- 3.4 Quasi-Cubic Approximation.- 3.5 Confined States.- 3.6 Conduction Band.- 3.7 Valence Band.- 3.8 Exciton Binding Energy in Quantum Wells.- 3.9 Polarization Effects.- 3A Appendix.- 4. Growth of Nitride Semiconductors.- 4.1 Bulk Growth.- 4.2 Substrates Used.- 4.2.1 Conventional Substrates.- 4.2.2 Compliant Substrates.- 4.2.3 Van der Waals Substrates.- 4.3 Substrate Preparation.- 4.4 Substrate Temperature.- 4.5 Epitaxial Relationship to Sapphire.- 4.6 Growth by Hydride Vapor Phase Epitaxy (HVPE).- 4.7 Growth by OMVPE (MOCVD).- 4.7.1 Sources.- 4.7.2 Buffer Layers.- 4.7.3 Lateral Growth.- 4.7.4 Growth on Spinel (MgAl2O4).- 4.8 Molecular Beam Epitaxy.- 4.8.1 MBE Growth Systems.- 4.8.2 Plasma-Enhanced MBE.- 4.8.3 Reactive-Ion MBE.- 4.8.4 Reactive MBE.- 4.8.5 Modeling of the MBE-Like Growth.- 4.9 Growth on 6H-SiC (0001).- 4.10 Growth on ZnO.- 4.11 Growth on GaN.- 4.12 Growth of p-Type GaN.- 4.13 Growth of n-Type InN.- 4.14 Growth of n-Type Ternary and Quaternary Alloys.- 4.15 Growth of p-Type Ternary and Quaternary Alloys.- 4.16 Critical Thickness.- 5. Defects and Doping.- 5.1 Dislocations.- 5.2 Stacking-Fault Defects.- 5.3 Point Defects and Autodoping.- 5.3.1 Vacancies, Antisites and Interstitials.- 5.3.2 Role of Impurities and Hydrogen.- 5.3.3 Optical Signature of Defects in GaN.- 5.4 Intentional Doping.- 5.4.1 n-Type Doping with Silicon, Germanium and Selenium.- 5.4.2 p-Type Doping.- a) Doping with Mg.- 5.4.3 Optical Manifestation of Group-II Dopant-Induced Defects in GaN.- a) Doping with Beryllium.- b) Doping with Mercury.- c) Doping with Carbon.- d) Doping with Zinc.- e) Doping with Calcium.- f) Doping with Rare Earths.- 5.4.4 Ion Implantation and Diffusion.- 5.5 Defect Analysis by Deep-Level Transient Spectroscopy.- 5.6 Summary.- 6. Metal Contacts to GaN.- 6.1 A Primer for Semiconductor-Metal Contacts.- 6.2 Current Flow in Metal-Semiconductor Junctions.- 6.2.1 The Regime Dominated by Thermionic Emission.- 6.2.2 Thermionic Field-Emission Regime.- 6.2.3 Direct Tunneling Regime.- 6.2.4 Leakage Current.- 6.2.5 The Case of a Forward-Biased p-n Junction.- 6.3 Resistance of an Ohmic Contact.- 6.3.1 Specific Contact Resistivity.- 6.3.2 Semiconductor Resistance.- 6.4 Determination of the Contact Resistivity.- 6.5 Ohmic Contacts to GaN.- 6.5.1 Non-Alloyed Ohmic Contacts.- 6.5.2 Alloyed Ohmic Contacts.- 6.5.3 Multi-Layer Ohmic Contacts.- 6.6 Structural Analysis.- 6.7 Observations.- 7. Determination of Impurity and Carrier Concentrations.- 7.1 Impurity Binding Energy.- 7.2 Conductivity Type: Hot Probe and Hall Measurements.- 7.3 Density of States and Carrier Concentration.- 7.4 Electron and Hole Concentrations.- 7.5 Temperature Dependence of the Hole Concentration.- 7.6 Temperature Dependence of the Electron Concentration.- 7.7 Multiple Occupancy of the Valence Bands.- 7A Appendix: Fermi Integral.- 8. Carrier Transport.- 8.1 Ionized Impurity Scattering.- 8.2 Polar-Optical Phonon Scattering.- 8.3 Piezoelectric Scattering.- 8.4 Acoustic Phonon Scattering.- 8.5 Alloy Scattering.- 8.6 The Hall Factor.- 8.7 Other Methods Used for Calculating the Mobility in n-GaN.- 8.8 Measured vis. a vis. Calculated Mobilities in GaN.- 8.9 Transport in 2D n-Type GaN.- 8.10 Transport in p-Type GaN and AlGaN.- 8.11 Carrier Transport in InN.- 8.12 Carrier Transport in AlN.- 8.12.1 Transport in Unintensionally-Doped and High-Resistivity GaN.- 8.13 Observation.- 9. The p-n Junction.- 9.1 Heterojunctions.- 9.2 Band Discontinuities.- 9.2.1 GaN/AIN Heterostructures.- 9.2.2 GaN/InN and AIN/InN.- 9.3 Electrostatic Characteristics of p-n Heterojunctions.- 9.4 Current-Voltage Characteristics on p-n Junctions.- 9.4.1 Generation-Recombination Current.- 9.4.2 Surf ace Effects.- 9.4.3 Diode Current Under Reverse Bias.- 9.4.4 Effect of the Electric Field on the Generation Current.- 9.4.5 Diffusion Current.- 9.4.6 Diode Current Under Forward Bias.- 9.5 Calculation and Experimental I-V Characteristics of GaN Based p-n Juctions.- 9.6 Concluding Remarks.- 10. Optical Processes in Nitride Semiconductors.- 10.1 Absorption and Emission.- 10.2 Band-to-Band Transitions.- 10.2.1 Excitonuc Transitions.- 10.3 Optical Transitions in GaN.- 10.3.1 Excitonic Transitions in GaN.- a) Free Excitons.- b) Bound Excitons.- c) Exciton Recombination Dynamics.- d) High Injection Levels.- 10.3.2 Free-to-Bound Transitions.- 10.3.3 Donor-Acceptor Transitions.- 10.3.4 Defect-Related Transitions.- a) Yellow Luminescence.- b) Group-II Element Related Transitions.- 10.4 Optical Properties of Nitride Heterostructures.- 10.4.1 GaN/AlGaN Heterostructures.- 10.4.2 InGaN/GaN and InGaN/InGaN Heterostructures.- 11. Light-Emitting Diodes.- 11.1 Current-Conduction Mechanism in LED-Like Structures.- 11.2 Optical Output Power.- 11.3 Losses and Efficiency.- 11.4 Visible-Light Emitting Diodes.- 11.5 Nitride LED Performance.- 11.6 On the Nature of Light Emission in Nitride-Based LEDs.- 11.6.1 Pressure Dependence of Spectra.- 11.6.2 Current and Temperature Dependence of Spectra.- 11.6.3 I-V Characteristics of Nitride LEDs.- 11.7 LED Degradation.- 11.8 Luminescence Conversion and White- Light Generation With Nitride LEDs.- 11.9 Organic LEDs.- 12. Semiconductor Lasers.- 12.1 A Primer to the Principles of Lasers.- 12.2 Fundamentals of Semiconductor Lasers.- 12.3 Waveguiding.- 12.3.1 Analytical Solution to the Waveguide Problem.- 12.3.2 Numerical Solution of the Waveguide Problem.- 12.3.3 Far-Field Pattern.- 12.4 Loss and Threshold.- 12.5 Optical Gain.- 12.5.1 Gain in Bulk Layers.- 12.5.2 Gain in Quantum Wells.- 12.6 Coulombic Effects.- 12.7 Gain Calculations for GaN.- 12.7.1 Optical Gain in Bulk GaN.- 12.7.2 Gain in GaN Quantum Wells.- 12.7.3 Gain Calculations in Wz GaN QW Without Strain.- 12.7.4 Gain Calculations in WZ QW With Strain.- 12.7.5 Gain in ZB QW Structures Without Strain.- 12.7.6 Gain in ZB QW Structures with Strain.- a) Pathways Through Excitons and Localized States.- 12.7.7 Measurement of Gain in Nitrides.- a) Gain Measurement via Optical Pumping.- b) Gain Measurement via Electrical Injection (Pump) and an Optical Probe.- 12.8 Threshold Current.- 12.9 Analysis of Injection Lasers with Simplifying Assumptions.- 12.10 Recombination Lifetime.- 12.11 Quantum Efficiency.- 12.12 Gain Spectra of InGaN Injection Lasers.- 12.13 Observations.- 12.14 A Succinct Review of the Laser Evolution in Nitrides.- References.