Growth and properties of GaAs/AlGaAs on nonpolar substrates using molecular beam epitaxy

Abstract

Using molecular beam epitaxy, we have successfully grown device quality GaAs/AlGaAs on (100)-oriented Ge and Si substrates. Modulation doped field effect transistors have been fabricated from these layers which exhibit room-temperature transconductances as high as 160 and 170 mS/mm for layers on Ge and Si, respectively, and showed no looping in either case. At 77 K, these values rose to 345 and 275 mS/mm for Ge and Si, respectively. Analysis by transmission electron microscopy of layers grown on Ge showed that the antiphase disorder was contained within the 250-Å-thick initial layer which was grown at a 0.1-μ/h growth rate at a substrate temperature of 500 °C. For both the layers grown on Si and Ge specular surface morphologies were obtained. The photoluminescence of GaAs/AlGaAs quantum wells grown on Si and Ge was similar in intensity to the same quantum well structures grown on GaAs. In quantum wells grown on Ge, the luminescence was dominated by a donor-acceptor recombination at 1.479 eV, which appears to be Ge0Ga -Ge0As. These results show that high-quality GaAs/AlGaAs is obtainable on nonpolar substrates, which has important implications for the monolithic integration of III-V’s with Si.