Nanorelief of an oxidized cleaved surface of a grid of alternating Ga0.7Al0.3As and GaAs heterolayers

The morphology of an oxidized cleaved surface of a grid of alternating GaAs and Ga 0.7 Al 0.3 As layers was investigated by atomic-force microscopy. It was found that the surface of the native oxide film on a cleaved surface possesses a quasistationary nanorelief that reflects the composition of the layers of the heterostructure. The oxide regions above the GaAlAs layers are 0.5 nm higher than the regions above the GaAs layers. Etching off the oxide film shows that a nanorelief, which is inverted with respect to the relief of the oxide surface, also forms on the bared cleaved surface. The appearance of nanoreliefs on the surface and at the bottom boundary of the native oxide film is explained by the different oxidation depths of GaAs and Ga 0.7 Al 0.3 As and by an oxidation-induced increase in the volume.