Atomic layer epitaxy of AlAs: Growth mechanism

Using a pulsed-jet method and trimethylaluminum (TMAl) and arsine (AsH3) sources, we studied atomic layer growth of AlAs(100). When we changed the source-gas pulse duration, we observed two- and three-monolayer saturation in the growth rate at 500°C, two-monolayer saturation at 473°C and three-monolayer saturation at 500°C. These saturation thicknesses correspond to the dominant surface phases of Al on arsenic-terminated surfaces. The activation energy of dissociative adsorption of TMAl on an arsenic-terminated surface was estimated to be 35 kcal/mol from the temperature dependence of the growth rate. We found overshooting in the growth rate in the TMAl pulse-duration dependence, which suggested that two- and three-dimensional Al phases on the growing surface at the same time, and that they changed from one phase to another with time and the Al surface coverage. We could explain these results with a new model including a phase-transition induced desorption (PTID) mechanism.