Effects of high-temperature annealing on the structural and crystalline qualities of GaAs heteroepitaxial layers grown on Si substrates using two-step and direct methods by molecular-beam epitaxy

The structural and crystalline qualities of GaAs/Si heteroepitaxial layers (heteroepilayers) were remarkably improved by annealing at temperatures above 900 °C, independently of the growth methods, either two-step or direct. The effects of high-temperature annealing on the optical property, residual strain, and the relation of the improvement in the quality with the out-diffusion of Si from the substrates and with vacancies in the GaAs heteroepilayers have been systematically investigated by a series of measurements using photoluminescence spectroscopy secondary-electron microscopy, double-crystal X-ray diffraction, secondary-ion mass spectroscopy and cross-sectional transmission electron microscopy.