半導体における電子なだれ現象

抄録

Electronic avalanche phenomena in semiconductors are described mainly in the view of ionization coefficient. The electric field dependence of the ionization coefficient in most of semiconductors can be surprisingly well fitted with Baraff's theory which has unified the lucky-electron model of Shockley and the diffusion approximation of Wolff. Electronic ava-lanche was so far an undesirable effect which deteriorates the junction characteristics, such as breakdown voltage and junction noise. But now, the avalanche phenomena are positively utilized to develop IMPATT diodes and avalanche photodiodes. In the high field domain of bulk effect devices, impact ionization also presents many interesting problems. To improve properties of IMPATT diode and bulk effect devices, more elaborate understanding of the avalanche phenomena is required.