Hadis Morkoç 
Handbook of Nitride Semiconductors and Devices, GaN-based Optical and Electronic Devices [PDF ebook] 

Preface XI

Color Tables XIX

1 Light-Emitting Diodes and Lighting 1

Introduction 1

1.1 Current-Conduction Mechanism in LED-Like Structures 4

1.2 Optical Output Power 6

1.3 Losses and Efficiency 7

1.4 Current Crowding 11

1.5 Packaging 15

1.6 Perception of Visible Light and Color 22

1.7 Visible-Light Terminology 27

1.7.1 Luminous Efficacy 29

1.7.2 Chromaticity Coordinates and Color Temperature 30

1.8 Inroads by LEDs 33

1.9 Nitride LED Performance 37

1.9.1 LEDs on Sapphire Substrates 38

1.9.1.1 Blue and Green LEDs 40

1.9.1.2 Amber LEDs 47

1.9.1.3 UV LEDs 48

1.9.1.4 Resonant Cavity-Enhanced LED 55

1.9.1.5 Effect of Threading Dislocation on LEDs 57

1.9.2 LEDs on Si C Substrates 60

1.9.3 LEDs on Si Substrates 61

1.9.4 LEDs Utilizing Rare Earth Transitions 62

1.10 On the Nature of Light Emission in Nitride-Based LEDs 64

1.10.1 Pressure Dependence of Spectra 65

1.10.2 Current and Temperature Dependence of Spectra 67

1.11 LED Degradation 70

1.12 LED Efficiency 76

1.13 Monochrome Applications of LEDs 82

1.14 Luminescence Conversion and White-Light Generation with Nitride LEDs 85

1.14.1 Color as Related to White-Light LEDs 87

1.14.2 Color Rendering Index 88

1.15 Approaches to White-Light Generation 91

1.15.1 White Light from Three-Chip LEDs 91

1.15.2 White Light from Four-Chip LEDs 97

1.15.3 Combining LEDs and Phosphor(s) 100

1.15.4 Other Photon Conversion Schemes 111

1.16 Toward the White-Light Applications 114

1.17 Organic/Polymeric LEDs (OLED, PLED) 122

1.17.1 OLED Structures 124

1.17.2 Charge and Energy Transport Fundamentals 132

1.17.3 Properties of Organic Crystals 135

1.17.4 Light Emission Dynamics 139

1.17.4.1 Nonradiative Recombination 143

1.17.4.2 Internal Conversion 143

1.17.4.3 Intersystem Crossing 143

1.17.4.4 Singlet Fission 143

1.17.4.5 Aggregation and Davydov Splitting 144

1.17.4.6 Charge-Transfer Excitons 145

1.17.5 OLED Devices 146

1.17.5.1 White OLEDs 147

1.17.5.2 Displays 151

1.17.6 Lighting with OLEDs 155

References 157

2 Semiconductor Lasers 169

Introduction 169

2.1 A Primer to the Principles of Lasers 172

2.2 Waveguiding 175

2.2.1 Refractive Index of Ga N and Al Ga N 176

2.2.2 Refractive Index of In Ga N 180

2.2.3 Analytical Solution to the Waveguide Problem 180

2.2.4 Numerical Solution of the Waveguide Problem 184

2.2.5 Far-Field Pattern 191

2.3 Loss, Threshold, and Cavity Modes 194

2.4 Optical Gain 196

2.4.1 A Glossary for Semiconductor Lasers 208

2.4.2 Optical Gain in Bulk Layers: A Semiconductor Approach 215

2.4.2.1 Relating Absorption Rate to Absorption Coefficient 216

2.4.2.2 Relating Stimulated Emission Rate to Absorption Coefficient 217

2.4.2.3 Relating Spontaneous Emission Rate to Absorption Coefficient 217

2.4.2.4 Fermi.s Golden Rule, Stimulated and Spontaneous Emission Rates, and Absorption Coefficient Within the k-Selection Rule 217

2.4.3 Gain in Quantum Wells 231

2.5 Coulombic Effects 235

2.6 Numerical Gain Calculations for Ga N 239

2.6.1 Optical Gain in Bulk Ga N 239

2.6.2 Gain in Ga N Quantum Wells 241

2.6.3 Gain Calculations in Wz Ga N Q Wells Without Strain 241

2.6.4 Gain Calculations in Wz Q Wells with Strain 241

2.6.5 Gain in ZB Q Wells Without Strain 244

2.6.6 Gain in ZB Q Wells with Strain 245

2.6.6.1 Pathways Through Excitons and Localized States 246

2.6.7 Measurement of Gain in Nitride Lasers 257

2.6.7.1 Gain Measurement via Optical Pumping 258

2.6.7.2 Gain Measurement via Electrical Injection (Pump) and Optical Probe Method 261

2.7 Threshold Current 262

2.8 Analysis of Injection Lasers with Simplifying Assumptions 263

2.9 Recombination Lifetime 264

2.10 Quantum Efficiency 267

2.11 Ga N-Based LD Design and Performance 267

2.12 Gain Spectra of In Ga N Injection Lasers 280

2.13 Near-UV Lasers 290

2.14 Reflector Stacks and Vertical Cavity Surface-Emitting Lasers (VCSELs) 293

2.15 Polariton Lasers 308

2.16 Ga In NAs Quaternary Infrared Lasers 312

2.17 Laser Degradation 315

2.18 Applications of Ga N-Based Lasers to DVDs 327

2.19 A Succinct Review of the Laser Evolution in Nitrides 330

References 334

3 Field Effect Transistors and Heterojunction Bipolar Transistors 349

Introduction 349

3.1 Heterojunction Field Effect Transistors 352

3.1.1 Electron Transport Properties in Ga N and Ga N/Al Ga N Heterostructures 353

3.1.2 Heterointerface Charge 356

3.1.3 Electromechanical Coupling 366

3.1.4 Analytical Description of HFETs 369

3.1.4.1 Examples for Ga N and In Ga N Channel HFETs 375

3.1.5 Numerical Modeling of Sheet Charge and Current 389

3.1.6 Numerically Calculated I–V Characteristics 398

3.2 The s-Parameters and Gain 401

3.3 Equivalent Circuit Models, Deembedding, and Cutoff Frequency 417

3.3.1 Small-Signal Equivalent Circuit Modeling 420

3.3.2 Large-Signal Equivalent Circuit Modeling 434

3.3.2.1 Nonlinearities 436

3.3.2.2 Dispersion and Temperature Effects 447

3.3.3 Cutoff Frequency 454

3.4 HFET Amplifier Classification and Efficiency 457

3.5 Al Ga N/Ga N HFETs 463

3.5.1 Experimental Performance of Ga N FETs 465

3.5.2 Power Amplifiers and Low-Noise Amplifiers (LNAs) 478

3.5.3 Drain-Voltage and Drain-Breakdown Mechanisms 483

3.5.4 Field Plate For Spreading Electric Field to Increase Breakdown Voltage 494

3.5.5 Anomalies in Ga N MESFETs and Al Ga N/Ga N HFETs 497

3.5.5.1 Effect of the Traps in the Buffer Layer 500

3.5.5.2 Effect of Barrier States 509

3.5.5.3 Field-Assisted Emission from the Barrier Traps 516

3.5.5.4 Defect Mapping by Kelvin Probe and Effect of Surface States 520

3.6 Electronic Noise 531

3.6.1 Shot Noise 532

3.6.2 Generation–Recombination Noise 533

3.6.3 Thermal Noise 534

3.6.4 Avalanche Noise 536

3.6.5 Low-Frequency Noise (1/f Noise) 537

3.6.5.1 Nonfundamental 1/f Noise 537

3.6.5.2 Fundamental 1/f Noise 538

3.6.6 High-Frequency Noise 541

3.6.7 Treatment of Noise with FET Equivalent Circuit 544

3.6.8 1/f Noise in Conjunction with Ga N FETs 550

3.6.9 High-Frequency Noise in Conjunction with Ga N FETs 558

3.7 Dielectrics for Passivation Purposes or Gate Leakage Reduction 563

3.8 Heat Dissipation and Junction Temperature 570

3.9 Hot Phonon Effects 577

3.9.1 Phonon Decay Channels and Decay Time 581

3.9.1.1 LO Phonon Decay Channels in Wurtzitic Ga N 584

3.9.1.2 Implications for FETs 593

3.10 In Ga N Channel and/or In Al N Barrier HFETs 609

3.11 FET Degradation 612

3.11.1 Reliability Measurements 617

3.11.2 Ga N HFET Reliability 619

3.11.2.1 Gate Current 624

3.11.2.2 Metallurgical Issues 628

3.11.2.3 Hot Electron and Hot Phonon Issues 629

3.11.2.4 Other Reliability Issues 633

3.12 Heterojunction Bipolar Transistors 635

3.12.1 HBT Fundamentals 638

3.12.1.1 Current Transport Mechanism Across the Heterojunction 639

3.12.1.2 Current Transport Mechanism Across Base 648

3.12.1.3 Electron Velocity Overshoot in the Collector Space Charge Region 657

3.12.1.4 Current Gain and Recombination Current of HBTs 659

3.12.1.5 Current Gain at High Currents 661

3.12.1.6 Emitter Current Crowding Effect 662

3.12.1.7 Noise in Bipolar Transistors 662

3.12.2 Nitride-Based HBTs 665

3.13 Concluding Comments 671

3.14 Appendix: Sheet Charge Calculation in Al Ga N/Ga N Structures with Al N Interface Layer (Al Ga N/Al N/Ga N) 672

References 675

4 Ultraviolet Detectors 709

Introduction 709

4.1 Principles of Photodetectors 713

4.1.1 Current and Voltage Response to Incident Radiation 718

4.1.1.1 Photoconductive Detectors 719

4.1.1.2 p–n-Junction Photovoltaic Detectors 720

4.1.2 Noise in Detectors 729

4.1.2.1 Thermal Noise 729

4.1.2.2 Shot Noise 730

4.1.2.3 Generation–Recombination Noise 731

4.1.2.4 1/f Noise 731

4.1.3 Quantum Efficiency 733

4.1.3.1 Quantum Efficiency in Photoconductors 733

4.1.3.2 Quantum Efficiency in a p–n-Junction Detector 734

4.1.4 Responsivity 738

4.1.5 Signal-to-Noise Ratio, Noise Equivalent Power, and Detectivity 738

4.1.5.1 Thermal Limited 740

4.1.5.2 Shot Current Limited 740

4.1.5.3 Generation–Recombination Limited 740

4.1.5.4 Background Radiation Limited 741

4.1.5.5 Noise in a p–n-Junction Detector 741

4.1.5.6 Detectivity for a p–n-Junction Detector 742

4.1.6 Surface and Bulk Recombination in Detectors 743

4.2 Particulars of Deep UV Radiation and Detection 744

4.2.1 Solar UV Radiation 746

4.2.2 Stratospheric Ozone and UV Absorption 747

4.2.3 Computational Method Called Plexus 747

4.2.4 UV Transmission of the Atmosphere 748

4.2.5 Number of Solar UV Photons Reaching Lower Altitudes 749

4.2.6 Atmospheric Detection Range 751

4.2.7 Inevitable and Unavoidable Losses of Photons 754

4.2.8 Practical UV Sensor Detection Ranges 756

4.2.9 Available UV Sensors 757

4.2.10 Design Requirements for UV Solar-Blind Imaging Detectors 759

4.3 Si and Si C-Based UV Photodetectors 762

4.3.1 Silicon-Based UV Photodetectors 763

4.3.2 Si C-Based UV Photodetectors 764

4.4 Nitride-Based Detectors 767

4.4.1 Photoconductive Detectors 768

4.4.2 Photovoltaic Detectors and Junction Detectors 775

4.4.2.1 Ga N and Al Ga N-Based Schottky Barrier Photodiodes 776

4.4.2.2 Metal–Semiconductor–Metal Detectors 782

4.4.2.3 p–n- and p-i-n-Junction Detectors 789

4.4.2.4 Al Ga N/Ga N Heterojunction Detectors 796

4.4.2.5 Al Ga N Detectors Including the Solar-Blind Variety 801

4.4.2.6 Al Ga N/Ga N MQW Photodetectors 806

4.4.2.7 Heterojunction Phototransistors 808

4.4.2.8 Ga N Avalanche Photodetectors 810

4.5 UV Imagers 814

4.6 Concluding Comments 819

References 820

Index 831

Appendix 847

Hadis Morkoç received his Ph.D. degree in Electrical Engineering from Cornell University. From 1978 to 1997 he was with the University of Illinois, then joined the newly established School of Engineering at the Virginia Commonwealth University in Richmond. He and his group have been responsible for a number of advancements in Ga N and devices based on them. Professor Morkoç has authored several books and numerous book chapters and articles. He serves or has served as a consultant to some 20 major industrial laboratories. Professor Morkoç is, among others, a Fellow of the American Physical Society, the Material Research Society, and of the Optical Society of America.