Vibrational signatures of OTe and OTe–VCd in CdTe: A first-principles study

Chen et al. [Phys. Rev. Lett. 96 (2006) 035508] experimentally observed vibrational signatures related to defects in oxygen-doped CdTe using ultrahigh resolution Fourier transform infrared (FTIR) spectroscopy. They observed an absorption peak at 350 cm−1. In addition, for samples grown under certain conditions, they observed two higher frequency peaks (1097 and 1108 cm−1) at low temperature that merged into one at room-temperature. They attributed the low-frequency peak (350 cm−1) to the vibration of OTe and the two higher frequency peaks to the vibrational modes of a OTe–VCd complex. Subsequently, they reported similar modes around 1100 cm−1 in O-doped CdSe [Phys. Rev. Lett. 101 (2008) 195502] which were attributed to an OSe–VCd complex. We employed first-principles DFT calculations to calculate the vibrational modes of OTe and OTe–VCd complex in CdTe. Our calculations show that the 350 cm−1 mode is consistent with OTe. However, the frequencies of the modes around 1100 cm−1 are more than twice the expected frequencies for OTe–VCd complexes in CdTe (or OSe–VCd in CdSe), indicating that the OTe–VCd complex cannot be the cause of the observed 1100 cm−1 modes. A search for a new defect model is in order.