8. The Bipolar Transistor……… 1. Introduction and basic principles 8. 1. Long-base device 252 8.1.2. Short-base device...,.,. 8.1.3. Fabrication process 8. 2. Amplification using a bipolar transistor 8.3. Ebers-Moll model 259 8.3. 1. Emitter efficiency 269 8.4. Regimes of operatic 272 8.5. Transport model 8.6. Gummel-Poon model 275 8.6.1. Current gai 280 8.6.1.1. Recombination in the base .... 280 8.6. 1 2. Emitter efficiency and current gain 282 erect 8.8. Dependence of current gain on collector current 8.8.1. Recombination at the emitter-base junction. 290 8. 8.2. Kirk effect 92 89. Base resistance 8.10. Numerical simulation of the bipolar transistor…………295 8.11. Collector junction breakdown…………………,298 8. 1. Common-base configuration 8.11. 2. Common-emitter configura 8.12. Charge- control model…… 812.1. Forward active mode 8.12. 2 Large-signal model 306 8. 12.3. Small-signal model Important Equations Problems∴ 309 9. Heterojunction Devices 315 9. 1. Concept of a heterojunction 1. Energy band diagram 9. 2. Heterojunction bipolar transistor(HBT) 320 9. 2. High electron mobility transistor (HEMT)..... 9.3. Photonic Devices 324 9.3. 1 Light-emitting diode (led) 324 9.3.2. Laser diode Problems 330viii Contents 8. 8.1. 8.1.1. 8.1.2. 8.1.3. 8.2. 8.3. 8.3.1. 8.3.2. 8.4. 8.5. 8.6. 8.6.1. 8.6.1.1. 8.6.1.2. 8.7. 8.8. 8.8.1. 8.8.2. 8.9. 8.10. 8.11. 8.11.1. 8.11.2. 8.12. 8.12.1. 8.12.2. 8.12.3. 9. 9.1. 9.1.1. 9.2. 9.2. 9.3. 9.3.1. 9.3.2. The Bipolar Transistor Introduction and basic principles Long-base device Short-base device Fabrication process Amplification using a bipolar transistor Ebers-Moll model Emitter efficiency Transport factor in the base Regimes of operation Transport model Gummel-Poon model Current gain Recombination in the base Emitter efficiency and current gain Early effect Dependence of current gain on collector current Recombination at the emitter-base junction Kirk effect Base resistance Numerical simulation of the bipolar transistor Collector junction breakdown Common-base configuration Common-emitter configuration Charge-control model Forward active mode Large-signal model Small-signal model Important Equations Problems Heterojunction Devices Concept of a heterojunction Energy band diagram Heterojunction bipolar transistor (HBT) High electron mobility transistor (HEMT) Photonic Devices Light-emitting diode (LED) Laser diode Problems 251 251 252 253 256 258 259 268 269 272 273 275 280 280 282 286 290 290 292 295 295 298 298 299 300 301 306 307 309 309 315 315 316 320 321 324 324 326 330