INITIAL-STAGES OF GE/GAAS(100) INTERFACE FORMATION

The initial stages of formation of the Ge/GaAs(100) interface have been investigated by monitoring, using low-energy electron diffraction and scanning tunneling microscopy (STM), the structural changes of the GaAs(100) surface after submonolayer germanium deposition and annealing. The distribution of Ge atoms on the GaAs(100)-(2 x 4) surface is random when the substrate temperature is below 600 K. After annealing at about 700 K, a poorly ordered (2 x 1) LEED pattern is observed which is attributed to Ge-As dimerization. When annealed above 825 K, a well-ordered, stable surface with a (1 x 2) superstructure is obtained, suggesting the formation of Ge-Ga dimer bonds. These results demonstrate the usefulness of STM in monitoring changes in the interfacial atomic structures during the initial stages of heteroepitaxy, which is an essential step in understanding and controlling other important interfacial properties, such as energy band offset.