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 GaA s and Al(0.42)Ga(0.56)AS at low temperatures (similar to 200 degrees C ), very strong and sustained reflection high-energy electron-diffracti on (RHEED) oscillations have been observed. Both the period and intens ity 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 t he two-dimensional (2D) growth mode, and the latter decreasing with in creasing arsenic supply, reflecting the creation of a barrier to 2D gr owth by the excess arsenic. Under exact stoichiometric conditions, the quality of the GaAs and AlGaAs is comparable to those grown at high t emperatures. It is therefore surmized that nonstoichiometry in low-tem perature-grown GaAs can be overcome leading to the growth of stoichiom etric low temperature materials possessing properties similar to those of conventional high-temperature-grown layers. (C) 1995 American Inst itute of Physics.