The defect structure of Te-doped GaAs after zinc diffusion

Abstract

Transmission electron microscope observations of the changes in the defect structure of heavily Te-doped GaAs induced by the diffusion of zinc were described in an earlier paper. A model accounting for the general features of the diffusion induced defect structure was presented. However, a detailed model accounting for, in particular, the changes in the precipitate, line dislocation and faulted loop population was not presented due to insufficient data. In the present paper several separate sets of results are presented which not only strongly support the conclusions reached in the earlier paper but, in combination, also clarify the behaviour of the precipitates, line dislocations and faulted loops in the diffused volume. The precipitates have been shown to form during the diffusion and to contain zinc and, by inference, gallium as well. Furthermore it is thought that the line dislocations observed in the diffused region are produced as a result of stresses about the precipitates and subsequent climb in a high, interstitial atmosphere. Precipitate pinning then leads to their observed non-uniform distribution. Finally, the faulted loops are observed to become triangular and display asymmetry at the diffusion front and it is suggested that this is, primarily, due to the incorporation of zinc with the subsequent likelihood of their being electrically active.