Asymmetries in photoconductive properties of donor and acceptor impurities in silicon

Abstract

Asymmetries observed in the spectral response, photoionization cross sections, and recombination coefficients as a function of impurity binding energy between donor and acceptor impurities in silicon are presented. These asymmetries, which are not predicted by the hydrogenic effective mass theory, permit higher operational temperatures for a given peak wavelength response for infrared detectors based on donor impurities. The photoconductive asymmetries can be correlated with recently calculated asymmetries associated with nonlinear charge-screening effects which make charge screening more effective for point-charge donors than for acceptors in silicon. To more fully account for the photoconductive asymmetries, impurity potentials more realistic than point charges are needed, including the accurate variation of dielectric screening of the potential with position.