Growth Mechanism of GaAs during Migration-Enhanced Epitaxy at Low Growth Temperatures

The growth process of GaAs during migration-enhanced epitaxy at low temperatures is investigated using reflection high-energy electron diffraction. Observation of specular beam intensity during growth reveals that a flat growing surface is maintained at 300°C even when the number of Ga atoms deposited per cycle is not equal to the surface site number. The composition at the growing surface can deviate considerably from stoichiometry at low temperatures because of excess As adsorpt ion. This problem is avoided by optimizing the number of As 4 molecules deposited per cycle. The optimum number of As 4 molecules was discussed with respect to the number of Ga atoms on the growing surface.