Isoelectronic oxygen-related defect in CdTe crystals investigated using thermoelectric effect spectroscopy

An oxygen-related defect was studied in nominally undoped CdTe crystals grown by the high pressure Bridgman technique using thermo-electrical effect spectroscopy and first-principles band structure calculations. Based on the linear relationship between the oxygen concentration and the emitted charge from the defect level with an ionization energy E=0.184+/-0.011 eV and a capture cross section sigma=(7+/-4)x10(-17) cm(2) we show that the defect is an oxygen complex. Using thermal annealing experiments we show that the defect complex contains cadmium vacancies. Using first-principles band structure calculations we assign the defect level to the second ionization level of the isoelectronic oxygen-cadmium vacancy pair (O-Te-V-Cd)(-/2-).