Diffusion of chromium in gallium arsenide

Abstract

Both in-diffusion and out-diffusion experiments for Cr in GaAs have been performed, using radiotracer Cr so that profiles could be plotted. An analysis of the profiles shows that they can be explained on the basis of a model in which the Cr diffuses through the lattice interstitially. A simple interpretation of the solubility data implies that the Cr occurs on the group V site, in contradiction to previous work on the system. An attempt is made to resolve this paradox by considering the possible form of the Ga-As-Cr phase diagram at the temperatures used in these diffusions. Electrical measurements were also made on Cr-diffused samples. Interpretation of these measurements was difficult because conversion of the samples to p-type occurred during the experiment. It is demonstrated that this conversion was due to the heat treatment involved in the diffusion rather than to the introduction of Cr into the crystal. The electrical measurements are consistent with the idea that Cr introduces a deep acceptor level into GaAs.