Influence of ambient media on the out-diffusion of S from InP:S

Abstract

Liquid-encapsulated Czochralski-grown InP:S samples annealed for short times of 30 min in various ambients at 550 °C show diffusion fronts suggesting an extremely rapid out-diffusion of S. In phosphorus ambient, the effective diffusion coefficient is inversely proportional to the phosphorus vapor pressure. Such a strong dependence on phosphorus vapor pressure is at variance with the generally accepted substitutional-interstitial model. The out-diffusion is fastest in vacuum, followed by hydrogen and forming gas mixtures. In inert gas medium (He), it is substantially slower. Annealing in air suggests the rapid formation of an oxide mask with little or no out-diffusion. An Arrhenius plot of the temperature dependence of the diffusion coefficient D in vacuum anneals, yields a D of 4×105 exp(−2.16 eV/kT) in the temperature range of 350–500 °C. Anneals in vacuum at 450 °C with different orientations showed that the out-diffusion is nearly orientation independent except for the observed absence of diffusion from 〈111〉-In face. The kinetics of surface reactions appear to play a significant role on the rates of diffusion.