Preferential Desorption of Ga from Al_xGa_1-xAs Grown by Molecular Beam Epitaxy

Abstract

Substrate-temperature dependence of surface and bulk composition of Al x Ga 1- x As grown by molecular beam epitaxy has been studied by auger electron spectroscopy and photoluminescence. Ga desorption during epitaxial growth is not negligible at the substrate temperature above 650°C. The surface Ga density of as-grown Al x Ga 1- x As is less than that of the bulk due to the Ga desorption after Ga flux is stopped. When the epitaxial wafer is kept at the growth temperature (above 690°C) for a few minutes without Al and Ga fluxes and with As 4 flux, the surface is covered with approximately three monolayers of AlAs due to desorption of Ga.