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Published online by Cambridge University Press: 10 February 2011
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°C shows complete thermal stability to annealing at temperatures up to 600°C. 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 (>104 Ω-cm) have been observed in the same as-grown material. Sub-picosecond lifetimes have been measured previously in undoped material, but the low growth temperatures required produce a supersaturation of antisites allowing for significant hopping conductivity through the defect band in as-grown material, 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 possible by proceeding to higher growth temperatures. Thus, nonstoichiometric GaAs having a beneficial combination of thermal stability, short carrier lifetime and high resistivity can be fabricated