Solubility and lattice location of Au in CdTe by backscattering techniques

Abstract

The solubility of Au in CdTe, at 800°C and 900°C, has been determined as a function of P cd (stoichiometry), and the lattice location of the Au has been investigated by ion channeling (2 MeV, 4He +) techniques. The measured Au solubilities varied from ∼10 18cm −3 to ∼10 20cm −3 and were found to increase with increasing temperature and with decreasing cadmium partial pressure roughly as P − 1 3 cd . Lattice location studies showed that from ∼50% to ∼80% of the Au remained in a substitutional, dissolved state after quenching to room temperature. In addition, angular yield scans indicate that the substitutional fraction of the incorporated Au is displaced off lattice sites by ∼0·2 Å. No flux peaking was seen in the angular yield scans and the non-substitutiolial fraction of the incorporated Au, manifested at room temperature, may consist either of precipitated or (displaced) interstitial Au. Diffusion coefficients of Au in CdTe have been estimated at 900°C, at the extreme boundaries of the phase field, using the ion channeling technique. The results indicate that the Au diffusivity decreases markedly with increasing P cd. These observations are found to be consistent with a dissociative model for Au in CdTe in which the major native defects are doubly ionized cadmium Frenkel defects and approximately singly ionized substitutional Au.