SCANNING-TUNNELING-MICROSCOPY STUDIES OF GE/GAAS(100) INTERFACE FORMATION

Study of the Ge/GaAs(100) interface provides important information to aid in understanding the formation of elemental-compound semiconductor heterojunctions. Using scanning tunneling microscopy and other surface sensitive probes, the Ge/GaAs(100) interface formation was investigated. On a molecular-beam epitaxially grown GaAs(100)-(2 X 4) substrate, submonolayer coverage of Ge atoms converts the surface into a (1 X 2) superstructure after annealing above 825 K. This structure can be explained by the formation of Ge-Ga dimer rows along the [011BAR] direction. On a surface with a submonolayer coverage of Ge annealed at a lower temperature, rows along the [011] direction with poor (2 X 1) order have been observed, which are considered to be an intermediate structure formed by Ge-As dimers. On vicinal GaAs(100) surfaces, the Ge-Ga dimer (1 X 2) reconstruction reduces the step-kink density.