Molecular beam epitaxy growth of AlGaAs on the (631)-oriented GaAs substrates

The authors report the molecular beam epitaxy growth and characterization of AlGaAs/GaAs(631) heterostructures grown at different As-4 molecular beam equivalent pressures. The reflection high-energy electron diffraction patterns taken along the [-1 2 0] azimuth showed that the twofold reconstruction commonly observed during the GaAs-buffer layer growth is preserved during the AlGaAs deposition. The 10 K photoluminiscence (PL) characterization of the samples showed transitions related to the AlGaAs band edge, the incorporation of impurities, and deep centers. The temperature dependence of the band to band PL transition was fitted with the models developed by Varshni, Passler, and Vina. The intensity of the PL spectra drastically decreases as the As-4 pressure is increased. Photoreflectance (PR) spectroscopy also showed the best crystal quality for the sample grown at low As pressure. The authors obtained the built-in internal electric field strength and the band-gap energy from an analysis of the PR spectra close to the GaAs band edge employing the Franz-Keldysh model. (C) 2008 American Vacuum Society.