Native defects and oxygen and hydrogen-related defect complexes in CdTe: Density functional calculations

We study structural and electronic properties of various intrinsic and extrinsic defects in CdTe based on first-principles calculations. The focus is given to the role of these defects in the carrier compensation in semi-insulating CdTe, which is essential for the CdTe-based radiation detectors. The semi-insulating behavior of CdTe has been attributed to the Fermi level pinning near middle of the band gap by deep donors. These deep donors compensate shallow acceptors and are generally assumed to be Te antisites. However, we find that intrinsic defects, including the Te antisite, may not have a significant effect on the carrier compensation due either to lack of deep levels near midgap or to low defect concentration. We demonstrate instead that an extrinsic defect, O-Te-H complex, may play an important role in the carrier compensation in CdTe. Other hydrogen-related defects are also discussed. (C) 2008 American Institute of Physics. [DOI: 10.1063/1.3000562]