Defect Control in As-Rich GaAs

The incorporation of excess As in GaAs, grown by MBE at low temperatures, produces native defects such as As antisites (As sub Ga), As interstitials (As sub i) or Ga vacancies (V sub Ga). These point defects dilate the lattice; their concentrations increase with decreasing growth temperature and can be well reproduced by a careful control of the substrate temperature and the As/Ga flux ratio. We studied high p-doping with Be acceptors in order to achieve a larger ionization fraction of the As sub Ga. As a result, we developed thermally stable, nonstoichiometric GaAs with subpicosec trapping times, grown at 275 C. In low temperature (LT) GaAs:Be, carrier capture at As sub Ga(+) is not the only trapping mechanism; concentration is neither correlated to the Be nor to the measured trapping times. The thermally more stable LT-GaAs:Be offers new prospects for the application of As-rich GaAs in ultrafast optoelectronics. (Author)