The avalanche multiplication process in multilayer structures in relatively low electric field

The effect of the avalanche multiplication of carriers caused by impact ionization on the current through a semiconductor multilayer structure is considered. It is shown that separate impact ionization rates for the electrons and the holes do not give satisfactory results because of too complex and not convenient theoretical and experimental techniques involved. A “bipolar” rate of carriers impact ionization is introduced, by help of which a simple expression for the current through a collector junction is derived. Proceeding from this a technique of experimental study of the avalanche multiplication process for the case of low electrical fields is worked out. This technique permits to obtain an empirical dependence of the avalanche multiplication coefficient on the junction voltage. An expression is picked out for the dependence of the bipolar rate of impact ionization on the electrical field.