A study was made of the role of defect diffusion, from crystal surfaces, in the disordering of a multiple quantum well structure that was Si-doped during molecular beam epitaxial growth. The distribution of the native defects was deduced from photoluminescence spectroscopic, secondary ion mass spectrometric, and electrochemical C-V profiling data. No significant difference was observed between the Al-Ga interdiffusion coefficients of Si-doped and undoped superlattices when they were annealed with excess Ga. This was attributed to the lack of a source of group-III vacancies. Only a small fraction of the enhancement which was predicted to result from Si doping was observed when excess As was used instead. The largest Fermi-level enhancement was observed when no excess Ga or As was present in the evacuated ampoule. The results indicated that the crystal surface was both source and sink for the native defects which were known to mediate Al-Ga interdiffusion. Significant electrical compensation of the donors was observed after annealing in both As-rich or Ga-rich ambients. This was attributed to ionized group-III vacancy generation in the former case, and to Si atoms which moved from group-III to group-V sites in the latter case.

B.L.Olmsted, S.N.Houde-Walter: Applied Physics Letters, 1993, 63[8], 1131-3