DISORDERING AND COMPENSATION IN SI-DOPED ALGAAS/GAAS SUPERLATTICES USING GA-RICH AND AS-RICH ANNEALING AMBIENTS

We report on a study of the role of defect diffusion from the crystal surface in the disordering of a multiple quantum well structure that was Si-doped during MBE growth. The distribution of native defects was inferred from correlating the results of photoluminescence spectroscopy, secondary ion mass spectrometry, and electrochemical C-V profiling. No significant change was observed between the Al-Ga interdiffusion coefficients of Si-doped and undoped superlattices when annealed with excess Ga. This is attributed to the lack of a source of group III vacancies. Furthermore, only a small fraction of the enhancement predicted for the Si doping was observed when excess As was used instead. The largest Fermi-level enhancement was observed when no excess Ga or As was included in the evacuated ampoule. The results indicate that the crystal surface was the source and sink of the native defects known to mediate the Al-Ga interdiffusion. Furthermore, significant electrical compensation of the donors was observed after both As- and Ga-rich anneals. This is attributed to ionized group III vacancy generation in the former case, and Si atoms moving from groups III to V sites in the latter.