GaAs Epitaxy by a Molecular Beam Method: Observations of Surface Structure on the (001) Face

Abstract

The epitaxial growth of GaAs by a molecular beam deposition method on bromine-methanol etched (001) GaAs substrate has been studied in situ in an ultrahigh vacuum high-energy electron diffraction system. GaAs (001)−C(2×8) and (001)−C(8×2) surface structures were observed during growth: one is arsenic stabilized, the other is gallium stabilized, and they are rotated 90° about the [001] axis from each other. Which surface structure is present during growth is a function of the ratio of the arsenic to gallium intensity in the molecular beam and the substrate temperature. For a given As2/Ga ratio, there is a transition from growth with the arsenic-stabilized (001)−C(2×8) to the gallium-stabilized (001)−C(8×2) with an increase in substrate temperature. In the case of a constant substrate temperature, the same transition can be achieved by varying the As2/Ga ratio. Without the molecular beam impinging on the surface, a gallium-stabilized (001)−C(8×2) surface structure quenches to a (001)−6 structure while the arsenic-stabilized (001)−C(2×8) structure remains unchanged.