Effect of Electrostatic Field Gradient in Semiconductors with Diffused Impurities

Abstract

Previous works on the evaluation of the collection efficiency of diffused radiant energy converters have assumed a constant electrostatic field in the diffused region. In order to match the theoretical spectral response based on this assumption with the experimental results, extremely low values of minority carrier lifetime were further assumed. No physical explanation is available for these assumptions. Using the basic diffusion theory, a theoretical investigation of the effects of impurity distribution in diffused semiconductors has been carried out for diffused impurity profiles produced by (1) diffusion from an infinitesimally thin layer of dopant and (2) diffusion from a constant podant source. It has been established that the electrostatic field gradient in the diffused semiconductor acts as an equivalent recombination effect with an equivalent minority carrier lifetime of the order of 10−10 sec. It has been shown that the effect of an electrostatic field gradient is much more predominant than the radiative and nonradiative recombinations.