The diffusion of aluminium and gallium in zinc oxide

Abstract

Solubilities and rates of substitutional diffusion of aluminium and gallium in polycrystalline zinc oxide have been determined in the temperature range 750-1000° by a chemical method previously described. The solubility of aluminium in zinc oxide, expressed in ions cm^-3, is given by the expression n = 1.0 x 10²³exp(-1.08k^-1T^-1), and the solubility of gallium by n = 2.7 x 10²¹exp(-0.59k^-1T^-1), where the activation energies are expressed in eV. The rates of diffusion of both aluminium and gallium were found to be dependent on surface concentration up to a limiting value, at which the diffusion coefficient of aluminium is D = 5.3 x 10^-2 exp(-2.74k^-1T^-1) cm² sec^-1, and that of gallium is D = 3.6 x 10⁴ exp(-3.75k^-1T^-1) cm² sac^-1.     It is shown that supersaturation of both aluminium and gallium in the zinc oxide crystals occurs above 800°.