The effect of stoichiometry deviations upon the type and density of crystalline defects was studied. In particular, a study was made of extended defects and precipitates via preferential etching, high-resolution X-ray diffraction, double-crystal X-ray topography and cathodoluminescence. A marked difference was found between crystals grown from the vapour phase and from the melt. The dislocations were found to be arranged in cellular structures which were 2 to 300μm in diameter, while precipitates were homogeneously distributed on the growth plane. The cathodoluminescence spectra exhibited an intense near-bandedge emission throughout the entire range of temperatures, with 2 large emission bands that were centered at 1.2 and 1.4eV. It was observed that the luminescence intensity of the 1.4eV band increased close to crystal defects, and the near-bandedge intensity simultaneously decreased. The disappearance of this emission from the cathodoluminescence spectra and from the cathodoluminescence images, upon increasing the temperature to 300K, suggested that a donor–acceptor pair transition was involved.

Defect-Induced Luminescence in High-Resistivity High-Purity Undoped CdTe Crystals. N.Armani, C.Ferrari, G.Salviati, F.Bissoli, M.Zha, A.Zappettini, L.Zanotti: Journal of Physics - Condensed Matter, 2002, 14[48], 13203-9