Behavior and mechanism of wide terrace formation during metalorganic vapor phase epitaxy of GaAs and related materials

Abstract

We have investigated the behavior and mechanism of surface terrace formation during the annealing of GaAs in the presence of column-V gases and during the growth of GaAs, Al 0.35Ga 0.65As and AlAs by metalorganic vapor phase epitaxy (MOVPE) using atomic force microscopy. The ordered terrace arrays with monolayer-high steps are formed during annealing in arsine prior to growth. The width of the terraces formed during growth depends on the substrate misorientation angle. The critical terrace widths for two-dimensional nucleation for GaAs and AlGaAs are found to be similar, but those for AlAs are narrower. The widths for GaAs and AlGaAs grown by MOVPE are about one or two orders of magnitude larger than the widths for GaAs and Al 0.3Ga 0.7As grown by molecular beam epitaxy. However, a wide GaAs terrace is not formed when trimethylarsine (TMAs) is used as a column-V source. To explain wide terrace formation in MOVPE, we propose a hydrogen-radical terminated surface model and obtain results supporting this model. Hydrogen radicals generated from the decomposition of arsine enhance the surface of column-III species on H-terminated As atoms.