Low-temperature GaAs films grown on Ge and Ge/SiGe/Si substrates

Abstract

The growth and structural properties of low-temperature GaAs (LT-GaAs) films grown on Ge/SiGe/Si substrates using solid-source molecular-beam epitaxy were investigated. Identical structures were also grown on both Ge and GaAs substrates in order to ascertain the effects of heterovalent interfaces, lattice mismatch, and surface morphology on the structural properties and excess As incorporation of LT-GaAs. Triple-axis x-ray diffraction measurements revealed nearly identical lattice expansion due to excess As incorporation for LT-GaAs layers on all substrates, with the excess As concentration estimated to be 0.34%. Subsequent in situ annealing resulted in complete layer relaxation coupled with the formation of randomly distributed As precipitates of similar sizes throughout the LT-GaAs layers on each substrate as determined by transmission electron microscopy. Secondary ion mass spectroscopy measurements confirmed the incorporation of excess As to be identical for growth on each substrate type, indicating that LT-GaAs with ideal structural properties can be grown on compositionally graded SiGe/Si substrates with no apparent impact from crosshatched surface morphology or heterovalent interfaces.