Thermal stabilizaiton of nonstoichiometric GaAs through beryllium doping

摘要

Beryllium-doped, non-stoichiometric GaAs grown by MBE at low temperatures appears superior to its undoped counterpart in several key areas vital to device manufacturing. X-ray diffraction studies have indicated that material grown above 275 deg shows complete thermal stability to annealing to temperatures up to 600 deg. This behavior is ascribed in part to strain compensation between the small beryllium atoms and the large arsenic antisites. Consequently, outdiffusion of excess arsenic from the non-stoichiometric material into neighboring layers upon annealing or subsequent high temperature growth is expected to be negligible. Short carrier lifetime (<1 psec) and high resistivity (> 10~4 #OMEGA#-cm) have been observed in the same as-grown material. Subpicosecond lifetimes have been measured previously inundoped material, but the low growth temepratures required produce a supersaturation of antisites allowing for significant hoppeing conductivity through the defect band in as-grown mateial, and significant arsenic outdiffusion upon annealing. Due to electrical compensation of antisites by beryllium acceptors, materials in which the ionized antisites represent a major fraction of a relatively small total antisite concentration are now made posible by proceeding to higher growth temperatures. Thus, non-stoichiometric GaAs having a beneficial combination of thermal stability, short carrier lifetime and high resistivity can be fabricated.