After Zn diffusion into Si-doped material, the diffused samples were annealed in vacuum, in As vapor, or with a Si3N4 mask capping the surface. The Zn concentration profiles which were obtained by secondary ion mass spectroscopy, and photoluminescence spectra for various depths below the sample surface, were studied in detail. After annealing in vacuum, the steep (p+-n) Zn diffusion front advanced into the bulk. It was observed that the intensity ratio between the Si donor-Ga vacancy complex (SiGa-VGa) related emission band and the band-to-band (e-h) transition was enhanced in the region ahead of the Zn diffusion front. On the other hand, Zn atoms diffused deeper into the bulk of samples which were annealed in As vapor, with or without a capping layer. These samples exhibited kink-and-tail (p+-p-n ) Zn concentration profiles with a decrease in the intensity ratio around the tail region. Analysis of the photoluminescence data suggested that there was a supersaturation of Ga vacancies ahead of the diffusion front of samples which were annealed in vacuum, and an under-saturation of this defect around the tail region of samples which were annealed in As vapor. The results emphasized the important role which was played by non-equilibrium of the defect concentration during post-diffusion annealing. This permitted an anomalous Zn double profile to be explained in terms of the interstitial-substitutional mechanism.

Effects of Post-Diffusion Annealing on Zn-Diffused GaAs:Si. N.H.Ky, J.D.Ganière, F.K.Reinhart, B.Blanchard, J.C.Pfister: Journal of Applied Physics, 1993, 74[9], 5493-500