An investigation was made of near-bandedge photoluminescence from semi-insulating crystals after they had been annealed in wafer or bulk form. The results, with respect to uniformity after annealing, were in agreement with previous data. The 1.360eV emission band which was seen in annealed crystals and which had been assumed to imply that a VAs-related rapid-diffusion process was the mechanism which was responsible for the annealing-induced uniformity, was shown to be unconnected with it. The involvement of VAs in the band was questioned. From literature data, it was estimated that the diffusion coefficient of VAs (1.2 x 10-12 at 1050C, 5.8 x 10-14 at 850C and 6.7 x 10-16cm2/s at 650C) was too low to permit bulk equilibrium and uniformity via vacancy diffusion from the surface at the annealing temperatures which were used. It was concluded that local rearrangement of defects was a viable mechanism for producing uniformity during post-growth annealing.

V.Swaminathan, R.Caruso, S.J.Pearton: Journal of Applied Physics, 1988, 63[6], 2164-7