The thermal oxidation of AlGaAs

There are many electronic and optoelectronic devices fabricated from Alx Ga1−x As and GaAs epitaxial layers. It is important to characterize the oxides that grow on these materials since the oxides can strongly influence the surface leakage currents and passivation properties of the devices. While all of the oxides of GaAs have been extensively studied, only the anodic oxides of AlGaAs have received much attention. This paper presents x-ray photoelectron spectroscopy results of the chemical composition of thermally grown Alx Ga1−x As oxides grown in O2 in the temperature range 450 °C to 600 °C for x=0.31 and 0.52. All of the oxides were found to have a complex structure consisting of three distinct layers. The outer layer is very thin and contains As, Ga and Al oxides, the middle layer is composed of Ga2 O3 and Al2 O3 in the same ratio as the AlGaAs substrate with a low concentration of elemental As. The interfacial layer contains only Al2 O3 and elemental As. A model is proposed to explain this multilayer growth.