Preface ...................................................... xvii
Acknowledgments ................................................ ix
About the Author .............................................. xxi
Part I: Fundaments of Infrared Detection ........................ 1
1 Radiometry .................................................... 2
1.1 Radiometric and Photometric Quantities and Units ........ 2
1.2 Definitions of Radiometric Quantities ................... 4
1.3 Radiance ................................................ 7
1.4 Blackbody Radiation .................................... 10
1.5 Emissivity ............................................. 13
1.6 Infrared Optics ........................................ 15
1.7 Some Radiometric Aspects of Infrared Systems ........... 17
1.7.1 Night-Vision System Concepts .................... 17
1.7.2 Atmospheric Transmission and Infrared Bands ..... 18
1.7.3 Scene Radiation and Contrast .................... 20
References .................................................. 21
2 Infrared Detector Characterization .......................... 23
2.1 Historical Aspects of Modern Infrared Technology ....... 24
2.2 Classification of Infrared Detectors ................... 28
2.3 Cooling of IR Detectors ................................ 31
2.3.1 Cryogenic Dewars ................................ 32
2.3.2 Joule-Thompson Coolers .......................... 32
2.3.3 Stirling Cycle Coolers .......................... 32
2.3.4 Peltier Coolers ................................. 33
2.4 Detector Figures of Merit .............................. 33
2.4.1 Responsivity .................................... 34
2.4.2 Noise Equivalent Power .......................... 34
2.4.3 Detectivity ..................................... 34
2.5 Fundamental Detectivity Limits ......................... 35
References .................................................. 40
3 Fundamental Performance Limitations of Infrared Detectors ... 45
3.1 Thermal Detectors ...................................... 45
3.1.1 Principle of Operation .......................... 45
3.1.2 Noise Mechanisms ................................ 48
3.1.3 Detectivity and Fundamental Limits .............. 49
3.2 Photon Detectors ....................................... 53
3.2.1 Photon Detection Process ........................ 53
3.2.2 Theoretical Model of Photon Detectors ........... 56
3.2.2.1 Optical Generation Noise ............... 58
3.2.2.2 Thermal Generation and Recombination
Noise .................................. 59
3.2.3 Optimum Thickness of Photodetector .............. 60
3.2.4 Detector Material Figure of Merit ............... 60
3.2.5 Reducing Device Volume to Enhance Performance ... 62
3.3 Comparison of Fundamental Limits of Photon and
Thermal Detectors ...................................... 65
3.4 Modeling of Photodetectors ............................. 69
References .................................................. 71
4 Heterodyne Detection ........................................ 75
References .................................................. 83
Part II: Infrared Thermal Detectors ............................ 87
5 Thermopiles ................................................. 88
5.1 Basic Principle and Operation of Thermopiles ........... 88
5.2 Figures of Merit ....................................... 91
5.3 Thermoelectric Materials ............................... 93
5.4 Micromachined Thermopiles .............................. 96
5.4.1 Design Optimization ............................. 97
5.4.2 Thermopile Configurations ....................... 98
5.4.3 Micromachined Thermopile Technology ............. 98
References ................................................. 101
6 Bolometers ................................................. 104
6.1 Basic Principle and Operation of Bolometers ........... 104
6.2 Types of Bolometers ................................... 107
6.2.1 Metal Bolometers ............................... 107
6.2.2 Thermistors .................................... 107
6.2.3 Semiconductor Bolometers ....................... 108
6.2.4 Micromachined Room Temperature Silicon
Bolometers ..................................... 1ll
6.2.5 Superconducting Bolometers ..................... 117
6.2.6 High-Temperature Superconducting Bolometers .... 121
6.3 Hot Electron Bolometers ............................... 126
References ................................................. 130
7 Pyroelectric Detectors ..................................... 138
7.1 Basic Principle and Operation of Pyroelectric
Detectors ............................................. 138
7.1.1 Responsivity ................................... 139
7.1.2 Noise and Detectivity .......................... 142
7.2 Pyroelectric Material Selection ....................... 144
7.2.1 Single Crystals ................................ 145
7.2.2 Pyroelectric Polymers .......................... 147
7.2.3 Pyroelectric Ceramics .......................... 147
7.2.4 Dielectric Bolometers .......................... 148
7.2.5 Choice of Material ............................. 152
7.3 Pyroelectric Vidicon .................................. 152
References ................................................. 153
8 Novel Thermal Detectors .................................... 157
8.1 Golay Cell ............................................ 157
8.2 Novel Uncooled Detectors .............................. 157
8.2.1 Electrically Coupled Cantilevers ............... 160
8.2.2 Optically Coupled Cantilevers .................. 163
8.2.3 Pyro-Optical Transducers ....................... 166
8.2.4 Antenna-Coupled Microbolometers ................ 168
8.3 Comparison of Thermal Detectors ....................... 169
References ................................................. 171
Part III: Infrared Photon Detectors ........................... 175
9 Theory of Photon Detectors ................................. 176
9.1 Photoconductive Detectors ............................. 176
9.1.1 Intrinsic Photoconductivity Theory ............. 176
9.1.2 Extrinsic Photoconductivity Theory ............. 185
9.1.3 Operating Temperature of Intrinsic and
Extrinsic Infrared Detectors ................... 194
9.2 p-n Junction Photodiodes .............................. 197
9.2.1 Ideal Diffusion-Limited p-n Junctions .......... 198
9.2.2 Real p-n Junctions ............................. 205
9.2.3 Response Time .................................. 213
9.3 p-i-n Photodiodes ..................................... 214
9.4 Avalanche Photodiodes ................................. 216
9.5 Schottky-Barrier Photodiodes .......................... 222
9.5.1 Schottky-Mott Theory and Its Modifications ..... 222
9.5.2 Current Transport Processes .................... 223
9.5.3 Silicides ...................................... 225
9.6 Metal-Semiconductor-Metal Photodiodes ................. 226
9.7 MIS Photodiodes ....................................... 227
9.8 Nonequilibrium Photodiodes ............................ 232
9.9 nBn Detector .......................................... 233
9.10 Photoelectromagnetic, Magnetoconcentration, and
Dember Detectors ...................................... 234
9.10.1 Photoelectromagnetic Detectors ................. 235
9.10.2 Magnetoconcentration Detectors ................. 239
9.10.3 Dember Detectors ............................... 240
9.11 Photon-Drag Detectors ................................. 242
References ................................................. 245
10 Intrinsic Silicon and Germanium Detectors .................. 256
10.1 Silicon Photodiodes ................................... 256
10.2 Germanium Photodiodes ................................. 264
10.3 SiGe Photodiodes ...................................... 266
References ................................................. 269
11 Extrinsic Silicon and Germanium Detectors .................. 272
11.1 Technology ............................................ 273
11.2 Peculiarities of the Operation of Extrinsic
Photodetectors ........................................ 274
11.3 Performance of Extrinsic Photoconductors .............. 276
11.3.1 Silicon-Doped Photoconductors .................. 276
11.3.2 Germanium-Doped Photoconductors ................ 278
11.4 Blocked Impurity Band Devices ......................... 280
11.5 Solid-State Photomultipliers .......................... 284
References ................................................. 285
12 Photoemissive Detectors .................................... 290
12.1 Internal Photoemission Process ........................ 290
12.1.1 Scattering Effects ............................. 294
12.1.2 Dark Current ................................... 296
12.1.3 Metal Electrodes ............................... 297
12.2 Control of Schottky-Barrier Detector Cutoff
Wavelength ............................................ 298
12.3 Optimized Structure and Fabrication of Schottky-
Barrier Detectors ..................................... 299
12.4 Novel Internal Photoemissive Detectors ................ 300
12.4.1 Heterojunction Internal Photoemissive
Detectors ...................................... 300
12.4.2 Homojunction Internal Photoemissive
Detectors ...................................... 301
References ................................................. 303
13 III-V Detectors ............................................ 309
13.1 Some Physical Properties of III-V Narrow Gap
Semiconductors ........................................ 309
13.2 InGaAs Photodiodes .................................... 315
13.2.1 p-i-n InGaAs Photodiodes ....................... 316
13.2.2 InGaAs Avalanche Photodiodes ................... 318
13.3 Binary III-V Detectors ................................ 321
13.3.1 InSb Photoconductive Detectors ................. 321
13.3.2 InSb Photoelectromagnetic Detectors ............ 322
13.3.3 InSb Photodiodes ............................... 324
13.3.4 InAs Photodiodes ............................... 331
13.3.5 InSb Nonequilibrium Photodiodes ................ 335
13.4 Ternary and Quaternary III-V Detectors ................ 337
13.4.1 InAs Sb Detectors .............................. 339
13.4.2 Photodiodes Based on GaSb-Related Ternary and
Quaternary Alloys .............................. 348
13.5 Novel Sb-Based III-V Narrow Gap Photodetectors ........ 350
13.5.1 InTlSb and InTIP ............................... 350
13.5.2 InSbBi ......................................... 351
13.5.3 InSbN .......................................... 352
References ................................................. 352
14 HgCdTe Detectors ........................................... 366
14.1 HgCdTe Historical Perspective ......................... 366
14.2 HgCdTe: Technology and Properties ..................... 369
14.2.1 Phase Diagrams ................................. 369
14.2.2 Outlook on Crystal Growth ...................... 370
14.2.3 Defects and Impurities ......................... 376
14.3 Fundamental HgCdTe Properties ......................... 379
14.3.1 Energy Bandgap ................................. 379
14.3.2 Mobilities ..................................... 380
14.3.3 Optical Properties ............................. 383
14.3.4 Thermal Generation-Recombination Processes ..... 387
14.4 Auger-Dominated Photodetector Performance ............. 391
14.4.1 Equilibrium Devices ............................ 391
14.4.2 Nonequilibrium Devices ......................... 392
14.5 Photoconductive Detectors ............................. 394
14.5.1 Technology ..................................... 394
14.5.2 Performance of Photoconductive Detectors ....... 396
14.5.3 Trapping-Mode Photoconductors .................. 402
14.5.4 Excluded Photoconductors ....................... 402
14.5.5 SPRITE Detectors ............................... 406
14.6 Photovoltaic Detectors ................................ 410
14.6.1 Junction Formation ............................. 411
14.6.2 Fundamental Limitation to HgCdTe Photodiode
Performance .................................... 420
14.6.3 Nonfundamental Limitation to HgCdTe
Photodiode Performance ......................... 432
14.6.4 Avalanche Photodiodes .......................... 437
14.6.5 Auger-Suppressed Photodiodes ................... 442
14.6.6 MIS Photodiodes ................................ 446
14.6.7 Schottky-Barrier Photodiodes ................... 448
14.7 Hg-Based Alternative Detectors ........................ 449
14.7.1 Crystal Growth ................................. 450
14.7.2 Physical Properties ............................ 451
14.7.3 HgZriTe Photodetectors ......................... 453
14.7.4 HgMnTe Photodetectors .......................... 454
References ................................................. 456
15 IV-VI Detectors ............................................ 485
15.1 Material Preparation and Properties ................... 485
15.1.1 Crystal Growth ................................. 485
15.1.2 Defects and Impurities ......................... 488
15.1.3 Some Physical Properties ....................... 489
15.1.4 Generation-Recombination Processes ............. 494
15.2 Polycrystalline Photoconductive Detectors ............. 498
15.2.1 Deposition of Polycrystalline Lead Salts ....... 498
15.2.2 Fabrication .................................... 499
15.2.3 Performance .................................... 501
15.3 p-n Junction Photodiodes .............................. 501
15.3.1 Performance Limit .............................. 502
15.3.2 Technology and Properties ...................... 507
15.4 Schottky-Barrier Photodiodes .......................... 514
15.4.1 Schottky-Barrier Controversial Issue ........... 514
15.4.2 Technology and Properties ...................... 517
15.5 Unconventional Thin Film Photodiodes .................. 522
15.5 Tunable Resonant Cavity Enhanced Detectors ............ 525
15.6 Lead Salts Versus HgCdTe .............................. 527
References ................................................. 529
16 Quantum Well Infrared Photodetectors ....................... 542
16.1 Low Dimensional Solids: Background .................... 542
16.2 Multiple Quantum Wells and Superlattices .............. 548
16.2.1 Compositional Superlattices .................... 548
16.2.2 Doping Superlattices ........................... 549
16.2.3 Intersubband Optical Transitions ............... 551
16.2.4 Intersubband Relaxation Time ................... 555
16.3 Photoconductive QWIP .................................. 556
16.3.1 Fabrication .................................... 557
16.3.2 Dark Current ................................... 558
16.3.3 Photocurrent ................................... 564
16.3.4 Detector Performance ........................... 566
16.3.5 QWIP versus HgCdTe ............................. 570
16.4 Photovoltaic QWIP ..................................... 573
16.5 Superlattice Miniband QWIPs ........................... 575
16.6 Light Coupling ........................................ 577
16.7 Related Devices ....................................... 580
16.7.1 p-Doped GaAs/AlGaAs QWIPs ...................... 580
16.7.2 Hot-Electron Transistor Detectors .............. 581
16.7.3 SiGe/Si QWIPs .................................. 582
16.7.4 QWIPs with Other Material Systems .............. 584
16.7.5 Multicolor Detectors ........................... 585
16.7.6 Integrated QWIP-LED ............................ 588
References ................................................. 589
17 Superlattice Detectors ..................................... 601
17.1 HgTe/HgCdTe Superlattice .............................. 601
17.1.1 Material Properties ............................ 601
17.1.2 Superlattice Photodiodes ....................... 604
17.2 Strained Layer Superlattices .......................... 608
17.3 InAsSb/InSb Strained Layer Superlattice Photodiodes ... 609
17.4 InAs/GaInSb Type II Strained Layer Superlattices ...... 611
17.4.1 Material Properties ............................ 611
17.4.2 Superlattice Photodiodes ....................... 615
17.4.3 nBn Superlattice Detectors ..................... 620
References ................................................. 622
18 Quantum Dot Infrared Photodetectors ........................ 629
18.1 QDIP Preparation and Principle of Operation ........... 629
18.2 Anticipated Advantages of QDIPs ....................... 631
18.3 QDIP Model ............................................ 632
18.4 Performance of QDIPs .................................. 638
18.4.1 R0A Product .................................... 638
18.4.2 Detectivity at 78 К ............................ 638
18.4.3 Performance at Higher Temperature .............. 639
References ................................................. 641
Part IV: Focal Plane Arrays ................................... 645
19 Overview of Focal Plane Array Architectures ................ 646
19.1 Overview .............................................. 646
19.2 Monolithic FPA Architectures .......................... 650
19.2.1 CCD Devices .................................... 653
19.2.2 CMOS Devices ................................... 657
19.3 Hybrid Focal Plane Arrays ............................. 660
19.3.1 Interconnect Techniques ........................ 660
19.3.2 Readout Integrated Circuits .................... 662
19.4 Performance of Focal Plane Arrays ..................... 665
19.4.1 Noise Equivalent Difference Temperature ........ 667
19.4.2 NEDT Limited by Readout Circuit ................ 670
19.5 Minimum Resolvable Difference Temperature ............. 673
19.6 Adaptive Focal Plane Arrays ........................... 673
References ................................................. 676
20 Thermal Detector Focal Plane Arrays ........................ 680
20.1 Thermopile Focal Plane Arrays ......................... 681
20.2 Bolometer Focal Plane Arrays .......................... 686
20.2.1 Manufacturing Techniques ....................... 689
20.2.2 FPA Performance ................................ 692
20.2.3 Packaging ...................................... 696
20.3 Pyroelectric Focal Plane Arrays ....................... 697
20.3.1 Linear Arrays .................................. 697
20.3.2 Hybrid Architecture ............................ 698
20.3.3 Monolithic Architecture ........................ 701
20.3.4 Outlook on Commercial Market of Uncooled
Focal Plane Arrays ............................. 703
20.4 Novel Uncooled Focal Plane Arrays ..................... 705
References ................................................. 707
21 Photon Detector Focal Plane Arrays ......................... 715
21.1 Intrinsic Silicon and Germanium Arrays ................ 715
21.2 Extrinsic Silicon and Germanium Arrays ................ 719
21.3 Photoemissive Arrays .................................. 725
21.4 III-V Focal Plane Arrays .............................. 731
21.4.1 InGaAs Arrays .................................. 731
21.4.2 InSb Arrays .................................... 735
21.5 HgCdTe Focal Plane Arrays ............................. 742
21.5.1 Monolithic FPAs ................................ 744
21.5.2 Hybrid FPAs .................................... 745
21.6 Lead Salt Arrays ...................................... 751
21.7 QWIP Arrays ........................................... 755
21.8 InAs/GaInSb SLS Arrays ................................ 759
References ................................................. 762
22 Terahertz Detectors and Focal Plane Arrays ................. 776
22.1 Direct and Heterodyne Terahertz Detection: General
Considerations ........................................ 778
22.2 Schottky-Barrier Structures ........................... 780
22.3 Pair-Braking Photon Detectors ......................... 784
22.4 Thermal Detectors ..................................... 786
22.4.1 Semiconductor Bolometers ....................... 787
22.4.2 Superconducting Hot-Electron Bolometers ........ 790
22.4.3 Transition Edge Sensor Bolometers .............. 792
22.5 Field Effect Transistor Detectors ..................... 795
22.6 Conclusions ........................................... 798
References ................................................. 799
23 Third-Generation Infrared Detectors ........................ 808
23.1 Benefits of Multicolor Detection ...................... 808
23.2 Requirements of Third-Generation Detectors ............ 810
23.3 HgCdTe Multicolor Detectors ........................... 812
23.3.1 Dual-Band HgCdTe Detectors ..................... 813
23.3.2 Three-Color HgCdTe Detectors ................... 821
23.4 Multiband QWIPs ....................................... 822
23.5 Type-II InAs/GaInSb Dual-Band Detectors ............... 832
23.6 Multiband QDIPs ....................................... 836
References ................................................. 839
Final Remarks ................................................. 846
Index ......................................................... 849
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