On the Theory of Optical Absorption Spectra of Disordered Semiconductors

Abstract

AbstractThe low frequency tails of the intrinsic and impurity optical absorption coefficients of nondegenerate semiconductors are calculated by the Green's functions method. The tails are due to the random force fields present in the samples. The fields are supposed to be generally anisotropic, Gaussian, and slowly varying in space. The intrinsic absorption tail has a Gaussian shape and a classical origin if the random fields acting upon electrons and holes are different. If the field is independent of the band index the absorption tail has a purely quantum origin; its shape depends somewhat upon the type of the field anisotropy and is close to exponential. As an example a special problem is considered in which the random field is provided by an intense acoustic noise flux propagating through the sample (both the deformation and the piezoelectrical interactions are considered). The results obtained are applied to interpret some experiments in which a modulation of an intrinsic absorption edge of piezocrystals by acoustoelectric domains was studied.