Here is a Sample Chapter of the book “Light Emitting Diodes, Second edition” by E. F. Schubert (Cambridge University Press, 2006).
Table of
Contents: Light Emitting Diodes, Second edition, 2006
1.1 History of SiC LEDs 1
1.2 History of GaAs and AlGaAs infrared and red LEDs 4
1.3 History of GaAsP LEDs 8
1.4 History of GaP and GaAsP LEDs doped with optically active impurities 9
1.5 History of GaN metal-semiconductor emitters 15
1.6 History of blue, green, and white LEDs based on GaInN p-n junctions 17
1.7 History of AlGaInP visible-spectrum LEDs 19
1.8 LEDs entering new fields of applications 21
References 23
2.1 Radiative electron-hole recombination 27
2.2 Radiative recombination for low-level excitation 28
2.3 Radiative recombination for high-level excitation 32
2.4 Bimolecular rate equations for quantum well structures 33
2.5 Luminescence decay 33
2.6 Non-radiative recombination in the bulk 35
2.7 Non-radiative recombination at surfaces 41
2.8 Competition between radiative and non-radiative recombination 44
3.3 Temperature and doping dependence of recombination 54
3.4 The Einstein model 56
References 57
4 LED basics: Electrical properties 59
4.1 Diode current–voltage characteristic 59
4.3 Evaluation of diode parasitic resistances 67
4.4 Emission energy 68
4.5 Carrier distribution in p-n homojunctions 69
4.6 Carrier distribution in p-n heterojunctions 70
4.7 Effect of heterojunctions on device resistance 71
4.8 Carrier loss in double heterostructures 75
4.9 Carrier overflow in double heterostructures 78
4.10 Electron-blocking layers 81
4.11 Diode voltage 83
References 84
5.1 Internal, extraction, external, and power efficiencies 86
5.2 Emission spectrum 87
5.3 The light escape cone 91
5.4 Radiation pattern 93
5.5 The lambertian emission pattern 94
5.6 Epoxy encapsulants 97
5.7 Temperature dependence of emission intensity 98
References 100
6 Junction and carrier temperatures 101
6.1 Carrier temperature and high-energy slope of spectrum 101
6.2 Junction temperature and peak emission wavelength 103
6.3 Theory of temperature dependence of diode forward voltage 104
6.4 Measurement of junction temperature using forward voltage 108
6.5 Constant-current and constant-voltage DC drive circuits 110
References 112
7.1 Double heterostructures 113
7.2 Doping of active region 116
7.3 p-n junction displacement 118
7.4 Doping of the confinement regions 119
7.5 Non-radiative recombination 122
7.6 Lattice matching 123
References 126
8 Design of current flow 127
8.1 Current-spreading layer 127
8.2 Theory of current spreading 133
8.3 Current crowding in LEDs on insulating substrates 136
8.4 Lateral injection schemes 140
8.5 Current-blocking layers 142
References 143
9 High extraction efficiency structures 145
9.1 Absorption of below-bandgap light in semiconductors 145
9.2 Double heterostructures 149
9.3 Shaping of LED dies 150
9.4 Textured semiconductor surfaces 154
9.5 Cross-shaped contacts and other contact geometries 156
9.6 Transparent substrate technology 157
9.7 Anti-reflection optical coatings 159
9.8 Flip-chip packaging 160
References 161
10 Reflectors 163
10.1 Metallic reflectors, reflective contacts, and transparent contacts 164
10.2 Total internal reflectors 168
10.3 Distributed Bragg reflectors 170
10.4 Omnidirectional reflectors 181
10.5 Specular and diffuse reflectors 184
References 189
11 Packaging 191
11.1 Low-power and high-power packages 191
11.2 Protection against electrostatic discharge (ESD) 193
11.3 Thermal resistance of packages 195
11.4 Chemistry of encapsulants 196
11.5 Advanced encapsulant structures 198
References 199
12.1 The GaAsP, GaP, GaAsP:N, and GaP:N material systems 201
12.2 The AlGaAs/GaAs material system 206
12.3 The AlGaInP/GaAs material system 209
12.4 The GaInN material system 211
12.5 General characteristics of high-brightness LEDs 213
12.6 Optical characteristics of high-brightness LEDs 216
12.7 Electrical characteristics of high-brightness LEDs 218
References 220
13.1 The UV spectral range 222
13.2 The AlGaInN bandgap 223
13.3 Polarization effects in III–V nitrides 224
13.4 Doping activation in III–V nitrides 226
13.5 Dislocations in III–V nitrides 227
13.6 UV devices emitting at wavelengths longer than 360 nm 231
13.7 UV devices emitting at wavelengths shorter than 360 nm 233
References 236
14.1 Modification of spontaneous emission 239
14.2 Fabry-Perot resonators 241
14.3 Optical mode density in a one-dimensional resonator 244
14.4 Spectral emission enhancement 248
14.5 Integrated emission enhancement 249
14.6 Experimental emission enhancement and angular dependence 251
References 253
15.1 Introduction and history 255
15.2 RCLED design rules 256
15.3 GaInAs/GaAs RCLEDs emitting at 930 nm 260
15.4 AlGaInP/GaAs RCLEDs emitting at 650 nm 265
15.5 Large-area photon recycling LEDs 268
15.6 Thresholdless lasers 270
15.7 Other RCLED devices 271
15.8 Other novel confined-photon emitters 272
References 273
16.1 Light receptors of the human eye 275
16.2 Basic radiometric and photometric units 277
16.3 Eye sensitivity function 280
16.4 Colors of near-monochromatic emitters 283
16.5 Luminous efficacy and luminous efficiency 284
16.6 Brightness and linearity of human vision 286
References 289
Appendix 16.1 Photopic eye sensitivity function 290
Appendix 16.2 Scotopic eye sensitivity function 291
17 Colorimetry 292
17.1 Color-matching functions and chromaticity diagram 292
17.2 Color purity 300
17.3 LEDs in the chromaticity diagram 301
17.4 Relationship between chromaticity and color 302
References 302
Appendix 17.1 Color-matching functions (CIE 1931) 304
Appendix 17.2 Color-matching functions (CIE 1978) 305
18 Planckian sources and color temperature 306
18.1 The solar spectrum 306
18.2 The planckian spectrum 307
18.3 Color temperature and correlated color temperature 309
References 311
Appendix 18.1 Planckian emitter 312
19 Color mixing and color rendering 313
19.1 Additive color mixing 313
19.2 Color rendering 315
19.3 Color-rendering index for planckian-locus illumination sources 323
19.4 Color-rendering index for non-planckian-locus illumination sources 324
References 327
Appendix 19.1 Reflectivity of test-color samples 328
Appendix 19.2 Reflectivity of test-color samples 330
20.1 Generation of white light with LEDs 332
20.2 Generation of white light by dichromatic sources 333
20.3 Generation of white light by trichromatic sources 338
20.4 Temperature dependence of trichromatic LED-based white-light source 340
20.5 Generation of white light by tetrachromatic and pentachromatic sources 344
References 344
21 White-light sources based on wavelength converters 346
21.1 Efficiency of wavelength-converter materials 347
21.2 Wavelength-converter materials 349
21.3 Phosphors 351
21.4 White LEDs based on phosphor converters 353
21.5 Spatial phosphor distributions 355
21.6 UV-pumped phosphor-based white LEDs 357
21.7 White LEDs based on semiconductor converters (PRS-LED) 358
21.8 Calculation of the power ratio of PRS-LED 359
21.9 Calculation of the luminous efficiency of PRS-LED 361
21.10 Spectrum of PRS-LED 363
21.11 White LEDs based on dye converters 364
References 364
22.1 Types of optical fibers 367
22.2 Attenuation in silica and plastic optical fibers 369
22.3 Modal dispersion in fibers 371
22.4 Material dispersion in fibers 372
22.5 Numerical aperture of fibers 374
22.6 Coupling with lenses 376
22.7 Free-space optical communication 379
References 381
23.1 LEDs for free-space communication 382
23.2 LEDs for fiber-optic communication 382
23.3 Surface-emitting Burrus-type communication LEDs emitting at 870 nm 383
23.4 Surface-emitting communication LEDs emitting at 1300 nm 384
23.5 Communication LEDs emitting at 650 nm 386
23.6 Edge-emitting superluminescent diodes (SLDs) 388
References 391
24 LED modulation characteristics 393
24.1 Rise and fall times, 3 dB frequency, and bandwidth in linear circuit theory 393
24.2 Rise and fall time in the limit of large diode capacitance 395
24.3 Rise and fall time in the limit of small diode capacitance 396
24.4 Voltage dependence of the rise and fall times 397
24.5 Carrier sweep-out of the active region 399
24.6 Current shaping 400
24.7 3 dB frequency 401
24.8 Eye diagram 401
24.9 Carrier lifetime and 3 dB frequency 402
References 403
Appendix 3 Room temperature properties of III–V arsenides 409
Appendix 4 Room temperature properties of III–V nitrides 410
Appendix 5 Room temperature properties of III–V phosphides 411
Appendix 6 Room temperature properties of Si and Ge 412
Appendix 7 Periodic system of elements (basic version) 413
Appendix 8 Periodic system of elements (detailed version) 414