High-purity GaAs grown by molecular-beam epitaxy

We have grown high-purity GaAs on (100), (311)A, and (311)B orientations by molecular-beam epitaxy (MBE). While undoped GaAs grown on (100) and (311)A are typically p type, growth on (311)B orientation has yielded n type with a liquid-nitrogen electron mobility of 1.3×105 cm2 V-1 s-1, which is among the highest mobilities reported for MBE-grown materials. Low-temperature photoluminescence showed well-resolved impurity bound exciton peaks consistent with electrical results. The possible incorporations of impurities, especially carbon, are discussed. Our work demonstrates that the previously reported undoped p-type GaAs(100) are compensated.