On the absence of decoration As precipitates at dislocations in Te-doped GaAs

This paper is aimed at explaining the absence of As precipitates decorating dislocations in Te-doped GaAs which are found instead when other dopants are used. By transmission electron microscopy it is seen that dislocations in Te-doped GaAs are always tangled and surrounded by clouds of extrinsic loops but are not decorated with any As precipitate. Diluted Sirtl-like etching used with light (DSL etching), micro-Raman and EBIC (electron-beam-induced-current) results support the conclusion that the regions containing the loop clusters around dislocations are enriched in the TeAsVGa acceptor complex that has formed due to the diffusion of Te towards the dislocation. The formation of TeAsVGa causes an undersaturation of Ga vacancies and hence the production of a supersaturation of Ga interstitials. The latter is the driving force for the formation of the observed extrinsic loops and dislocation tangling through climb. Such processes, however, consume As interstitials which are thus no longer available for the formation of decoration As precipitates. The peculiar characteristic of Te of forming acceptor complexes like TeAsVGa is discussed with reference to the group IV dopants.