A Study of the 0.1-EV Conversion Acceptor in GaAs

Two semi-insulating liquid-encapsulated Czochralski GaAs cyrstals, one Cr-doped and the other undoped, were annealed at 750°C for 15 min in flowing H2. Each sample converted to conducting p type in the near-surface region, due to the formation of acceptors at E∪ + 0.1 eV. We have studied this phenomenon by electrical, optical, and analytical profiling techniques, and have determined conclusively that the acceptors in our samples are not related to Mn accumulation, a commonly accepted explanation. It is argued that the O.I-e V center may arise from several possible sources, each exhibiting a VGa -like state at this energy