Wavelength dependent effective trap density in CdTe: evidence for the presence of two photorefractive species

Abstract

An accurate determination of the effective trap density in CdTe:V is performed using both counter-propagating (small grating spacing) and co-propagating (large grating spacing) two-wave mixing. This enhanced precision allows to show a variation of the effective trap density with wavelength. We show that such a change is explained when two traps both coupled to the conduction and the valence bands are present. New theoretical expressions for the electron-hole competition coefficient and Debye screening length are derived and used.