Optical and electrophysical properties of defects in high-purity CdTe

The electronic spectrum of defects formed in low-temperature synthesis and growth of high-purity CdTe[111]from the vapor phase of the starting components has been studied by the photoluminescence and photoconductivity methods, as well as using the analysis of the behavior with temperature of the conductivity. The studies have revealed in the crystals, in addition to the comparatively shallow centers involving primarily donors and acceptors contained in residual substitutional impurities, deep acceptor states with activation energies of 0.25, 0.60, and 0.86 eV, which differ in the character and magnitude of the localizing potential. While the deep centers at 0.60 and 0.86 eV display strong localization of electronic states, the center with the 0.25-eV activation energy is associated with defects for which the major part of the localizing potential extends uniformly in space over several unit cells. Such centers are assumed to originate from twinning-induced extended defects.