DIFFUSION OF ZINC IN GAAS

The diffusion of zinc into GaAs at 1000°C, at dissociation pressure and under excess arsenic pressure is described. A technique using very small amounts of radio-active zinc was developed and the Boltzman-Matano method for analysis of diffusion profiles was extended to low zinc concentrations. The diffusion coefficient was generally found to vary in the extrinsic region as the square of the zinc concentration, as predicted by the substitutional-interstitial mechanism for diffusion. At high concentrations a maximum was reached for the diffusion coefficient. This can be attributed to a breakdown in the vacancy equilibrium. In the intrinsic region the coefficient tended to a constant value which was larger in the case of the dissociation pressure diffusions than in that of the excess arsenic diffusions by a factor of about three. This suggests that the substitutional-interstitial mechanism continues to operate at least down to a concentration of 1017 cc. © 1969.