Real-time observations of faceting and shrinkage processes of disk-shaped mesas in GaAs molecular beam epitaxy on GaAs (111) B substrates

We report the real-time observations of the faceting and the shrinkage processes of disk-shaped mesas in molecular beam epitaxy (MBE) of GaAs on (111)B substrates by micro-probe scanning electron microscopy (μ-RHEED/SEM) MBE system. It was found that the {110} and {221} facets are developed during the growth and finally the whole sides of surfaces were completely covered by three symmetric {110} facets. The top (111)B face became smaller and smaller due to the surface diffusion of Ga atoms from the side facets to the top and at last, the top size became very small. Real-time measurements of the top size were also made at different growth temperatures and arsenic pressures and it was found that the shrinkage rate of the top size greatly depends on the growth temperature, while at different arsenic pressures, the shrinkage rates are more or less similar.