Initial growth behaviors of disk-shaped mesas in GaAs molecular beam epitaxy on GaAs(111)B substrates

The real-time observations of initial growth behaviors were carried out in molecular beam epitaxy (MBE) of GaAs on disk-shaped mesa (111)B substrates by micro-probe reflection high-energy diffraction/scanning electron microscope (mu-RHEED/SEM) MBE system. It was found that the initial growth behavior depends strongly on the growth temperature. In the experiments, the initial growth process under different surface reconstructions (Ga stabilized (root 19 x root 19) and Ga-rich (1 x 1)(HT) surface reconstructions) was extensively studied. During the growth, it was found that {221} facets surrounding the foot of the mesas are formed at 580 and 610 degrees C, but the process and time for facet appearance are quite different. At 620 degrees C, the macrostep and associated black and white stripes composed of(root 19 x root 19) and (1 x 1)(HT) reconstructions were observed to propagate outward on the foot of the mesa, which resulted in the formation of gentle slopes with macrosteps. In the whole range of present growth temperature, it was found that Ga atoms diffuse from sidewalls to the bottom of the mesa especially in the beginning of the growth.