Real-time observations of mesa shrinkage process in MBE of GaAs on (1 1 1)B patterned substrates and theoretical analysis

Abstract

The faceting and shrinkage processes of mesa structures on GaAs (1 1 1)B substrates were monitored by microprobe reflection high-energy electron diffraction/scanning electron microscopy (microprobe-RHEED/SEM) installed in MBE chamber. To understand the experimental results, the calculation based on inter-surface diffusion model was conducted and the results are compared with the experiments. From the comparison we evaluated diffusion coefficient and incorporation lifetime of Ga adatoms. The lifetime and the diffusion coefficient of (1 1 1)B substrate were estimated, respectively, as 1/70 as small and 50 times as large as those of {1 1 0} side wall. The mesa shrinks faster when arsenic pressure is higher, because Ga adatoms on {1 1 0} side wall flow more towards (1 1 1)B top and less towards the bottom.