ISBN: 3-540-64038-X
TITLE: Nitride Semiconductors and Devices
AUTHOR: Morkoc, Hadis
TOC:

Foreword. A View of the Past, and a Look into the Future by a Pioneer 
By Jacques I. Pankove XV 
1. Introduction 1 
2. General Properties of Nitrides 8 
2.1 Crystal Structure of Nitrides 8 
2.2 Gallium Nitride 11 
2.2.1 Chemical Properties of GaN 13 
2.2.2 Thermal and Mechanical Properties of GaN 14 
2.3 Aluminum Nitride 17 
2.3.1 Thermal and Chemical Properties of AlN 17 
2.3.2 Mechanical Properties of AlN 19 
2.3.3 Electrical Properties of AlN 20 
2.3.4 Optical Properties of AlN 21 
2.4 Indium Nitride 23 
2.4.1 Crystal Structure of InN 24 
2.4.2 Mechanical and Thermal Properties of InN 25 
2.4.3 Electrical Properties of InN 25 
2.4.4 Optical Properties of InN 26 
2.5 Ternary and Quaternary Alloys 26 
2.5.1 AlGaN Alloy 27 
2.5.2 InGaN Alloy 29 
2.5.3 InAlN Alloy 31 
2.6 Substrates for Nitride Epitaxy 31 
2A Appendix Fundamental Data for Nitride Systems 39 
3. Electronic Band Structure 
of Bulk and QW Nitrides 45 
3.1 Band-Structure Calculations 45 
3.2 Effect of Strain on the Band Structure of GaN 51 
3.3 kp Theory and the Quasi-Cubic Model 52 
3.4 Quasi-Cubic Approximation 54 
3.5 Confined States 57 
3.6 Conduction Band 61 
3.7 Valence Band 63 
3.8 Exciton Binding Energy in Quantum Wells 66 
3.9 Polarization Effects 68 
3A Appendix 80 
4. Growth of Nitride Semiconductors 83 
4.1 Bulk Growth 84 
4.2 Substrates Used 87 
4.2.1 Conventional Substrates 88 
4.2.2 Compliant Substrates 88 
4.2.3 Van der Waals Substrates 89 
4.3 Substrate Preparation 89 
4.4 Substrate Temperature 94 
4.5 Epitaxial Relationship to Sapphire 95 
4.6 Growth by Hydride Vapor Phase Epitaxy (HVPE) 98 
4.7 Growth by OMVPE (MOCVD) 99 
4.7.1 Sources 100 
4.7.2 BufferLayers 102 
4.7.3 Lateral Growth 109 
4.7.4 Growth on Spinel (MgAl2O4) 112 
4.8 Molecular Beam Epitaxy 112 
4.8.1 MBE Growth Systems 113 
4.8.2 Plasma-Enhanced MBE 114 
4.8.3 Reactive-Ion MBE 117 
4.8.4 Reactive MBE 118 
4.8.5 Modeling of the MBE-Like Growth 125 
4.9 Growth on 6H-SiC (0001) 127 
4.10 Growth on ZnO 129 
4.11 Growth on GaN 136 
4.12 Growth of p-Type GaN 137 
4.13 Growth of n-Type InN 139 
4.14 Growth of n-Type Ternary and Quaternary Alloys 139 
4.15 Growth of p-Type Ternary and Quaternary Alloys 140 
4.16 Critical Thickness 141 
5. Defects and Doping 149 
5.1 Dislocations 150 
5.2 Stacking-Fault Defects 151 
5.3 Point Defects and Autodoping 153 
5.3.1 Vacancies, Antisites and Interstitials 154 
5.3.2 Role of Impurities and Hydrogen 160 
5.3.3 Optical Signature of Defects in GaN 163 
5.4 Intentional Doping 165 
5.4.1 n-Type Doping with Silicon, Germanium 
and Selenium 165 
5.4.2 p-Type Doping 167 
a) Doping with Mg 168 
5.4.3 Optical Manifestation 
of Group-II Dopant-Induced Defects in GaN 179 
a) Doping with Beryllium 182 
b) Doping with Mercury 182 
c) Doping with Carbon 183 
d) Doping with Zinc 184 
e) Doping with Caicium 184 
f) Doping with Rare Earths 184 
5.4.4 Ion Implantation and Diffusion 185 
5.5 Defect Analysis by Deep-Level Transient Spectroscopy 186 
5.6 Summary 190 
6. Metal Contacts to GaN 191 
6.1 A Primer for Semiconductor-Metal Contacts 192 
6.2 Current Flow in Metal-Semiconductor Junctions 196 
6.2.1 The Regime Dominated by Thermionic Emission 197 
6.2.2 Thermionic Field-Emission Regime 198 
6.2.3 Direct Tunneling Regime 199 
6.2.4 Leakage Current 200 
6.2.5 The Case of a Forward-Biased p-n Junction 200 
6.3 Resistance of an Ohmic Contact 202 
6.3.1 Specific Contact Resistivity 203 
6.3.2 Semiconductor Resistance 204 
6.4 Determination of the Contact Resistivity 206 
6.5 Ohmic Contacts to GaN 207 
6.5.1 Non-Alloyed Ohmic Contacts 208 
6.5.2 Alloyed Ohmic Contacts 209 
6.5.3 Multi-Layer Ohmic Contacts 209 
6.6 Structural Analysis 213 
6.7 Observations 215 
7. Determination of Impurity and Carrier Concentrations 216 
7.1 Impurity Binding Energy 216 
7.2 Conductivity Type: Hot Probe and Hall Measurements 217 
7.3 Density of States and Carrier Concentration 219 
7.4 Electron and Hole Concentrations 223 
7.5 Temperature Dependence of the Hole Concentration 224 
7.6 Temperature Dependence of the Electron Concentration 227 
7.7 Multiple Occupancy of the Valence Bands 229 
7A Appendix Fermi Integral 232 
8. Carrier Transport 233 
8.1 Ionized Impurity Scattering 235 
8.2 Polar-Optical Phonon Scattering 236 
8.3 Piezoelectric Scattering 239 
8.4 Acoustic Phonon Scattering 239 
8.5 Alloy Scattering 242 
8.6 The Hall Factor 248 
8.7 Other Methods Used for Calculating 
the Mobility in n-GaN 249 
8.8 Measured vis. a vis. Calculated Mobilities in GaN 251 
8.9 Transport in 2D n-Type GaN 257 
8.10 Transport in p-Type GaN and AlGaN 258 
8.11 Carrier Transport in InN 260 
8.12 Carrier Transport in AlN 262 
8.12.1 Transport in Unintensionally-Doped 
and High-Resistivity GaN 263 
8.13 Observation 266 
9. The pn Junction 267 
9.1 Heterojunctions 267 
9.2 Band Discontinuities 268 
9.2.1 GaN/AlN Heterostructures 270 
9.2.2 GaN/InN and AlN/InN 271 
9.3 Electrostatic Characteristics of p-n Heterojunctions 275 
9.4 Current-Voltage Characteristics on p-n Junctions 278 
9.4.1 Generation-Recombination Current 279 
9.4.2 Surface Effects 282 
9.4.3 Diode Current Under Reverse Bias 284 
9.4.4 Effect of the Electric Field 
on the Generation Current 284 
9.4.5 Diffusion Current 285 
9.4.6 Diode Current Under Forward Bias 287 
9.5 Calculation and Experimental I-V Characteristics 
of GaN Based p-n Juctions 288 
9.6 Concluding Remarks 294 
10. Optical Processes in Nitride Semiconductors 295 
10.1 Absorption and Emission 296 
10.2 Band-to-Band Transitions 300 
10.2.1 Excitonuc Transitions 302 
10.3 Optical Transitions in GaN 303 
10.3.1 Excitonic Transitions in GaN 303 
a) Free Excitons 303 
b) Bound Excitons 317 
c) Exciton Recombination Dynamics 318 
d) High Injection Levels 322 
10.3.2 Free-to-Bound Transitions 322 
10.3.3 Donor-Acceptor Transitions 323 
10.3.4 Defect-Related Transitions 326 
a) Yellow Luminescence 326 
b) Group-II Element Related Transitions 329 
10.4 Optical Properties of Nitride Heterostructures 331 
10.4.1 GaN/AlGaN Heterostructures 332 
10.4.2 InGaN/GaN and InGaN/InGaN Heterostructures 336 
11. Light-Emitting Diodes 340 
11.1 Current-Conduction Mechanism in LED-Like Structures 341 
11.2 Optical Output Power 344 
11.3 Losses and Efficiency 345 
11.4 Visible-Light Emitting Diodes 350 
11.5 Nitride LED Performance 352 
11.6 On the Nature of Light Emission in Nitride-Based LEDs 360 
11.6.1 Pressure Dependence of Spectra 360 
11.6.2 Current and Temperature Dependence of Spectra 363 
11.6.3 I-V Characteristics of Nitride LEDs 366 
11.7 LED Degradation 370 
11.8 Luminescence Conversion and White- Light Generation 
With Nitride LEDs 373 
11.9 Organic LEDs 376 
12. Semiconductor Lasers 379 
12.1 A Primer to the Principles of Lasers 381 
12.2 Fundamentals of Semiconductor Lasers 382 
12.3 Waveguiding 389 
12.3.1 Analytical Solution to the Waveguide Problem 390 
12.3.2 Numerical Solution of the Waveguide Problem 394 
12.3.3 Far-Field Pattern 402 
12.4 Loss and Threshold 405 
12.5 Optical Gain 406 
12.5.1 Gain in Bulk Layers 407 
12.5.2 Gain in Quantum Wells 410 
12.6 Coulombic Effects 413 
12.7 Gain Calculations for GaN 417 
12.7.1 Optical Gain in Bulk GaN 418 
12.7.2 Gain in GaN Quantum Wells 419 
12.7.3 Gain Calculations in Wz GaN QW Without Strain 419 
12.7.4 Gain Calculations in WZ QW With Strain 420 
12.7.5 Gain in ZB QW Structures Without Strain 423 
12.7.6 Gain in ZB QW Structures with Strain 424 
a) Pathways Through Excitons 
and Localized States 425 
12.7.7 Measurement of Gain in Nitrides 431 
a) Gain Measurement via Optical Pumping 431 
b) Gain Measurement via Electrical Injection 
(Pump) and an Optical Probe 437 
12.8 Threshold Current 439 
12.9 Analysis of Injection Lasers 
with Simplifying Assumptions 440 
12.10 Recombination Lifetime 442 
12.11 Quantum Efficiency 448 
12.12 Gain Spectra of InGaN Injection Lasers 450 
12.13 Observations 456 
12.14 A Succinct Review of the Laser Evolution in Nitrides 457 
References 461 
Subject Index 485 
END
