Energetics and electronic properties of interstitial chlorine in CdTe

Abstract

The role of interstitial chlorine in the electronic properties of CdTe isaddressed by density functional theory calculations including hybrid func-tionals and large unit cells. The stability and diffusion energy barriers of theimpurity are analyzed as a function of the Fermi level position in the bandgap. Chlorine is found to be stable in at least five interstitial sites with ratherclose formation energies, suggesting that they are all probable to be found.Inp-type CdTe, the most stable sites are at the center of a Cd─Te bond andat a split-interstitial configuration, both acting as shallow donors. Whereas inn-type CdTe, it is found at the tetrahedral site surrounded by Cd hosts, actingas a shallow acceptor. We also find that chlorine can induce a deep acceptorlevel in the bandgap after binding with three Cd host atoms, which canexplain the experimentally observed high resistivity in Cl-doped CdTe. Theenergy barriers for chlorine diffusion in bothp-type andn-type CdTe are alsodiscussed