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

The initial stages of formation of the Ge/GaAs(100) interface have bee n investigated by monitoring, using low-energy electron diffraction an d scanning tunneling microscopy (STM), the structural changes of the G aAs(100) surface after submonolayer germanium deposition and annealing . The distribution of Ge atoms on the GaAs(100)-(2 x 4) surface is ran dom 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 i s attributed to Ge-As dimerization. When annealed above 825 K, a well- ordered, stable surface with a (1 x 2) superstructure is obtained, sug gesting 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 ess ential step in understanding and controlling other important interfaci al properties, such as energy band offset.