Deep-level transient spectroscopy was used to study horizontal gradient freeze-grown n-type material that had been subjected to thermal stressing by quenching, and to various degrees of As out-diffusion during rapid thermal annealing. The concentrations and activation energies of the various deep donor levels were monitored. It was found that external excitations in the lattice, due to thermal stressing, had marked effects upon the defect level structure. Thus, the native EL6 group of defects was almost absent from rapid thermally annealed material, while the EL5 and EL8 levels appeared; with EL3 becoming a predominant level that could act as a recombination center. With increasing annealing time and, in the presence of appreciable As out-diffusion, there was a general reduction in the EL2, EL3, and EL5 defect concentrations; together with the complete removal of EL8. Also, the EL2 activation energy could be varied from 0.827 to 0.922eV by controlling the level of As out-diffusion. The observations were explained in terms of the AsGa-Asi model for the EL2 defect, and the VAs-VGa di-vacancy model for the EL6 group of defects. The EL3, EL5, EL8, and EL15 defect levels which were seen in samples that had been subjected to rapid thermal quenching were attributed to the break-up of the VAs-Asi Frenkel pair defects that were known to be present in as-grown material.

C.V.Reddy, S.Fung, C.D.Beling: Physical Review B, 1996, 54[16], 11290-7