Identification of oxygen defects in CdTe revisited: First-principles study

Abstract

Native defects and oxygen and hydrogen-related defect complexes in CdTe: Density functional calculations J. Appl. Phys.By using first-principles calculations, several SO 2 complexes in CdTe were studied. Based on experimental observation, SO 2 complexes have been recently proposed by Lavrov et al. [Phys. Rev. B. 84, 233201 (2011)] to be the cause of the observed IR absorption peaks at 1096.8 and 1108.4 cm À1 in O-doped CdTe. Chen et al. [Phys. Rev. Lett. 96, 035508 (2006)] were originally proposed that the peaks come from O Te -V Cd complex. Our calculations indicate that the SO 2 molecule on the Te site [(SO 2 ) Te ] has a low formation energy but its calculated vibration frequencies ($900 cm À1 ) are lower than the observed IR modes. However, (SO 2 ) Te can form a complex with V Cd with two possible configurations that give the vibration frequencies in a good agreement with the two observed IR peaks. The binding energies of the complex in these two configurations are about 1 eV under p-type conditions; indicating that the complex is quite stable. The two configurations are related to each other by a rotation of the SO 2 molecule with an energy barrier of $0.4 eV. Therefore, the two configurations can co-exist at a low temperature and the high energy one gradually transforms to the low energy one as temperature increases. This agrees with the experimental observation that, at a high temperature, the two IR modes merged into one. V C 2014 AIP Publishing LLC. [http://dx.

First-principlesDFT+GWstudy of oxygen-doped CdTe

“…Therefore, (O i ) is an electrically neutral defect and does not introduce any electronic level in the band gap of CdTe. Its formation energy is calculated to be 1.57 eV in the Te-rich limit and 2.27 eV in the Cd-rich limit, in agreement with recent DFT calculations [77].…”

“…This complex was initially pointed out as responsible for the local vibrational modes (LVMs) observed by Chen et al [78] via infrared spectroscopy. However, this assignment was later discarded by DFT calculations, which showed that the vibrational frequencies in the (O Te -V Cd ) complex are significantly lower than the two modes observed experimentally [25,77]. Our results indicate that this complex has a high formation energy, higher than (O Te ), (O Te -Te Cd ), and (O i ) in both Te-rich and Cd-rich conditions.…”