REAL-TIME OBSERVATION AND FORMATION MECHANISM OF GA DROPLET DURING MOLECULAR-BEAM EPITAXY UNDER EXCESS GA FLUX

Ga droplet formation during molecular beam epitaxy under excess Ga flux condition is observed in real time by a scanning electron microscope. The density of Ga droplets is measured under a wide range of both incident flux and growth temperature. It has been found that As, flux effectively reduces the density of droplets. As the growth temperature decreases the density increases abruptly around 500-degrees-C and exhibits a Ga flux dependence different from that of high temperature. Analyzing these results by nucleation theory, the basic parameters of the Ga droplet formation are obtained. It has been found that the formation of Ga droplets on GaAs surface is characterized by the Stranski-Krastanov mode.