Spontaneous growth of coherent tilted superlattice on vicinal (100) GaAs substrates

Abstract

Periodic Al composition modulations have been observed to occur spontaneously during molecular beam epitaxy of AlGaAs on vicinal (100) substrates. The formation of the spontaneous Al modulation requires (a) the migration-enhanced epitaxy deposition and (b) one monolayer deposition of Al and Ga atoms per cycle, hence, the denomination of coherent tilted superlattice (C-TSL). Cross-sectional transmission electron microscopy clearly shows that the C-TSL has the periodicity of the surface steps. We also show that the Al-rich regions of the C-TSL form at the bottom of steps before the As flux is established. These results indicate that growth kinetics dominates the C-TSL formation.