Series Preface ................................................ xxi
Preface ..................................................... xxiii
Foreword .................................................... xxvii
List of Contributors ......................................... xxxi
Part One - Growth ............................................... 1
1 Bulk Growth of Mercury Cadmium Telluride (MCT) ............... 3
P. Capper
1.1 Introduction ............................................ 3
1.2 Phase equilibria ........................................ 4
1.3 Crystal growth .......................................... 5
1.4 Conclusions ............................................ 18
References .................................................. 19
2 Bulk Growth of CdZnTe/CdTe Crystals ......................... 21
A. Noda, H. Kurita and R. Hirano
2.1 Introduction ........................................... 21
2.2 High-purity Cd and Те .................................. 22
2.3 Crystal growth ......................................... 23
2.4 Wafer processing ....................................... 41
2.5 Summary ................................................ 48
Acknowledgements ............................................ 48
References .................................................. 49
3 Properties of Cd(Zn)Te Relevant to Use as Substrates ........ 51
S. Adachi
3.1 Introduction ........................................... 52
3.2 Structural properties .................................. 52
3.3 Thermal properties ..................................... 55
3.4 Mechanical and lattice vibronic properties ............. 58
3.5 Collective effects and some response characteristics ... 61
3.6 Electronic energy-band structure ....................... 62
3.7 Optical properties ..................................... 67
3.8 Carrier transport properties ........................... 70
4 Substrates for the Epitaxial Growth of MCT .................. 75
J. Garland and R. Sporken
4.1 Introduction ........................................... 76
4.2 Substrate orientation .................................. 77
4.3 CZT substrates ......................................... 78
4.4 Si-based substrates .................................... 82
4.5 Other substrates ....................................... 89
4.6 Summary and conclusions ................................ 90
References .................................................. 90
5 Liquid Phase Epitaxy of MCT ................................. 95
P. Capper
5.1 Introduction ........................................... 95
5.2 Growth ................................................. 96
5.3 Material characteristics .............................. 103
5.4 Device status ......................................... 108
5.5 Summary and future developments ....................... 108
References ................................................. 110
6 Metal-Organic Vapor Phase Epitaxy (MOVPE) Growth ........... 113
C.D. Maxey
6.1 Requirement for epitaxy ............................... 113
6.2 History ............................................... 114
6.3 Substrate choices ..................................... 115
6.4 Reactor design ........................................ 117
6.5 Process parameters .................................... 118
6.6 Metal-organic sources ................................. 119
6.7 Uniformity ............................................ 120
6.8 Reproducibility ....................................... 120
6.9 Doping ................................................ 123
6.10 Defects ............................................... 125
6.11 Annealing ............................................. 127
6.12 In situ monitoring .................................... 127
6.13 Conclusions ........................................... 128
References ................................................. 128
7 MBE Growth of Mercury Cadmium Telluride .................... 131
J. Garland
7.1 Introduction .......................................... 131
7.2 MBE Growth theory and growth modes .................... 132
7.3 Substrate mounting .................................... 135
7.4 In situ characterization tools ........................ 135
7.5 MCT nucleation and growth ............................. 139
7.6 Dopants and dopant activation ......................... 141
7.7 Properties of MCT epilayers grown by MBE .............. 143
7.8 Conclusions ........................................... 146
References ................................................. 147
Part Two - Properties ......................................... 151
8 Mechanical and Thermal Properties .......................... 153
M. Martyniuk, J.M. Dell and L. Faraone
8.1 Density of MCT ........................................ 154
8.2 Lattice parameter of MCT .............................. 158
8.3 Coefficient of thermal expansion of MCT ............... 162
8.4 Elastic parameters of MCT ............................. 166
8.5 Hardness and deformation characteristics of MCT ....... 170
8.6 Phase diagrams of MCT ................................. 181
8.7 Viscosity of the MCT melt ............................. 187
8.8 Thermal properties of MCT ............................. 189
References ................................................. 197
9 Optical Properties of MCT ................................... 205
J. Chu and Y. Chang
9.1 Introduction .......................................... 205
9.2 Optical constants and the dielectric function ......... 206
9.3 Theory of band to band optical transition ............. 206
9.4 Near band gap absorption .............................. 207
9.5 Analytic expressions and empirical formulas for
intrinsic absorption and Urbach tail .................. 209
9.6 Dispersion of the refractive index .................... 216
9.7 Optical constants and related van Hover
singularities above the energy gap .................... 217
9.8 Reflection spectra and dielectric function ............ 220
9.9 Multimode model of lattice vibration .................. 221
9.10 Phonon absorption ..................................... 222
9.11 Raman scattering ...................................... 225
9.12 Photoluminescence spectroscopy ........................ 227
References ................................................. 231
10 Diffusion in MCT ........................................... 239
D. Shaw
10.1 Introduction .......................................... 239
10.2 Self-diffusion ........................................ 240
10.3 Chemical self-diffusion ............................... 243
10.4 Compositional interdiffusion .......................... 247
10.5 Impurity diffusion .................................... 253
11 Defects in HgCdTe - Fundamental ............................ 263
M.A. Berding
11.1 Introduction .......................................... 263
11.2 Native point defects in zincblende semiconductor ...... 264
11.3 Measurement of native defect properties and density ... 266
11.4 Ab initio calculations ................................ 268
11.5 Future challenges ..................................... 272
References ................................................. 272
12 Band Structure and Related Properties of HgCdTe ............ 275
C.R. Becker and S. Krishnamurthy
12.1 Introduction .......................................... 275
12.2 Parameters ............................................ 277
12.3 Electronic band structure ............................. 279
12.4 Comparison with experiment ............................ 288
13 Conductivity Type Conversion ............................... 297
D. Shaw and P. Capper
13.1 Introduction .......................................... 297
13.2 Native defects in undoped MCT ......................... 298
13.3 Native defects in doped MCT ........................... 301
13.4 Defect concentrations during cool down ................ 302
13.5 Change of conductivity type ........................... 304
13.6 Dry etching by IBM .................................... 307
13.7 Plasma etching ........................................ 313
13.8 Summary ............................................... 314
References ................................................. 315
14 Extrinsic Doping ........................................... 317
D. Shaw and P. Capper
14.1 Introduction .......................................... 318
14.2 Impurity activity ..................................... 319
14.3 Thermal ionization energies of impurities ............. 322
14.4 Segregation properties of impurities .................. 324
14.5 Traps and recombination centers ....................... 327
14.6 Donor and acceptor doping in LWIR and MWIR MCT ........ 330
14.7 Residual defects ...................................... 334
14.8 Conclusions ........................................... 335
References ................................................. 335
15 Structure and Electrical Characteristics of Metal/MCT
Interfaces ................................................. 339
R.J. Westerhout, R.H. Sewell, J.M. Dell, L. Faraone
and С.A. Musca
15.1 Introduction .......................................... 340
15.2 Reactive/intermediately reactive/nonreactive
categories ............................................ 341
15.3 Ultrareactive/reactive categories ..................... 344
15.4 Passivation of MCT .................................... 347
15.5 Contacts to MCT ....................................... 354
15.6 Surface Effects on MCT ................................ 356
15.7 Surface Structure of CdTe and MCT ..................... 359
References ................................................. 370
16 MCT Superlattices for VLWIR Detectors and Focal Plane
Arrays ..................................................... 375
J. Garland
16.1 Introduction .......................................... 376
16.2 Why HgTe-based superlattices .......................... 377
16.3 Calculated properties ................................. 384
16.4 Growth ................................................ 386
16.5 Interdiffusion ........................................ 389
16.6 Conclusions ........................................... 395
Acknowledgements ........................................... 396
References ................................................. 396
17 Dry Plasma Processing of Mercury Cadmium Telluride
and Related II-VIs ......................................... 399
A.J. Stoltz
17.1 Introduction .......................................... 400
17.2 Effects of plasma gases on MCT ........................ 401
17.3 Plasma parameters ..................................... 403
17.4 Characterization-surfaces of plasma-processed MCT ..... 411
17.5 Manufacturing issues and solutions .................... 416
17.6 Plasma processes in the production of II—VI
materials ............................................. 420
References ................................................. 425
18 MCT Photoconductive Infrared Detectors ..................... 429
I.M. Baker
18.1 Introduction .......................................... 429
18.2 Applications and sensor design ........................ 432
18.3 Photoconductive detectors in MCT and related alloys ... 434
18.4 SPRITE detectors ...................................... 440
18.5 Conclusions on photoconductive MCT detectors .......... 444
Acknowledgements ........................................... 445
References ................................................. 445
Part Three - Applications ..................................... 447
19 HgCdTe Photovoltaic Infrared Detectors ..................... 449
I.M. Baker
19.1 Introduction .......................................... 450
19.2 Advantages of the photovoltaic device in MCT .......... 450
19.3 Applications .......................................... 450
19.4 Fundamentals of MCT photodiodes ....................... 451
19.5 Theoretical foundations for MCT array technology ...... 454
19.6 Manufacturing technology for MCT arrays ............... 457
19.7 Towards GEN III detectors ............................. 463
19.8 Conclusions and future trends for photovoltaic MCT
arrays ................................................ 465
References ................................................. 465
20 Nonequilibrium, Dual-Band and Emission Devices ............. 469
C. Jones and N. Gordon
20.1 Introduction .......................................... 469
20.2 Nonequilibrium devices ................................ 470
20.3 Dual-band devices ..................................... 476
20.4 Emission devices ...................................... 484
20.5 Conclusions ........................................... 489
References ................................................. 489
21 HgCdTe Electron Avalanche Photodiodes (EAPDs) .............. 493
I. Baker and M. Kinch
21.1 Introduction and applications ......................... 493
21.2 The avalanche multiplication effect ................... 494
21.3 Physics of MCT EAPDs .................................. 495
21.4 Technology of MCT EAPDs ............................... 504
21.5 Reported performance of arrays of MCT EAPDs ........... 506
21.6 LGI as a practical example of MCT EAPDs ............... 510
21.7 Conclusions and future developments ................... 511
References ................................................. 511
22 Room Temperature IR Photodetectors ......................... 513
J. Piotrowski and A. Piotrowski
22.1 Introduction .......................................... 513
22.2 Performance of room temperature infrared
photodetectors ........................................ 514
22.3 HgCdTe as a material for room temperature
photodetectors ........................................ 519
22.4 Photoconductive devices ............................... 522
22.5 РЕМ, magnetoconcentration, and Dember IR detectors .... 524
22.6 Photodiodes ........................................... 526
22.7 Conclusions ........................................... 535
References ................................................. 535
Index ......................................................... 539
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