Basic relations for calculating the photocurrents of transistor structures

General formulae for calculating the photocurrents of transistor structures caused by the effect of ionizing radiation on a semiconductor device, are obtained. Nonequilibrium carrier collection coefficients are calculated both in inverse and normal directions for two cases: for the uniform semiconductor region and for the semiconductor with built-in electric field. Presented are the dependences of stationary values of collection coefficient in the uniform semiconductor region on the ionization nonuniformity and in the semiconductor with built-up field on the field factor. Transient characteristics of collection coefficients are presented for both cases. The relations and characteristics obtained may be used for building-up the models of bipolar transistors allowing for the effect of ionizing radiation