Observation of Ga Metal Droplet Formation on Photolithographically Patterned GaAs (100) Surface by Droplet Epitaxy

A sharp contrast on the density and size of Ga metal droplets is observed on various photolithographically patterned GaAs (100). As clearly evidenced by high-resolution scanning electron microscope, Ga metal droplet density and size surprisingly differ on etched and unetched surfaces under an identical growth condition. The apparent contrast on the density and size of droplets is clearly observed at the interface between etched and unetched areas. Ga droplets exhibit much higher density and the size is much smaller on etched surface; meanwhile, the density is an order of magnitude lower and the size is much larger on unetched surface. Along different directions, [011] and [01-1], due to anisotropic surface diffusion, the density is about twice higher along [011] for the same strip pattern.