Temperature effect on surface flatness of molecular beam epitaxy homoepitaxial layers grown on nominal and vicinal (111)B GaAs substrates

Abstract

For the first time a comparison is made between the surface characteristics of layers simultaneously grown on nominal and on vicinal (111)B substrates under the 1×1 reconstruction regime which provides flat surfaces for both orientations. The influence of growth temperatures, 600 and 700 °C, on surface characteristics is thoroughly reviewed based on an atomic force microscopy study. This study yields additional insight into results already reported on growth mechanisms occurring along these two orientations for the 19×19 growth regime. For the nominal (111)B layers, it will be shown that monoatomic steps at the surfaces define large atomically flat plateaus at both temperatures. At 600 °C, growth will be shown to proceed mainly through the development of two-dimensional nuclei, which are limited in size to a critical value and can coalesce by a proximity effect. These nuclei will be shown to be much smaller at 700 °C, thereby turning the step flow into the main mechanism occurring at that temperature. For the vicinal orientation, monoatomic-stepped and step-bunched surfaces grown at 600 and 700 °C, respectively, will be obtained under our 1×1 growth conditions, the same as in the 19×19 regime.