Stoichiometric low-temperature GaAs and AlGaAs: A reflection high-energy electron-diffraction study

By careful control of the arsenic beam supply during the growth of GaAs and Al_0.42Ga_0.56As at low temperatures (∼200 °C), very strong and sustained reflection high-energy electron-diffraction (RHEED) oscillations have been observed. Both the period and intensity of the RHEED oscillations are shown to be a strong function of the arsenic overpressure with the former increasing with increase arsenic supply, reflecting a decrease in the number of atoms taking part in the two-dimensional (2D) growth mode, and the latter decreasing with increasing arsenic supply, reflecting the creation of a barrier to 2D growth by the excess arsenic. Under exact stoichiometric conditions, the quality of the GaAs and AlGaAs is comparable to those grown at high temperatures. It is therefore surmized that nonstoichiometry in low-temperature-grown GaAs can be overcome leading to the growth of stoichiometric low temperature materials possessing properties similar to those of conventional high-temperature-grown layers.