Influence of Etching Time on Nanostructure Evolution of Ga-Droplets on GaAs Substrate

The influence of the etching time on the nanostructures of the Ga-droplets, deposited on GaAs substrate in molecular beam epitaxy (MBE) reactor, was investigated with scanning tunneling microscope (STM). The preliminary results show that the etching time had a major impact. To be specific, Ga droplets were deposited on c (4×4) GaAs surfaces before the rapid re-crystallization involving As-deposition. In the first 5 min of Ga-droplet etching, oval discs formed at the Ga-droplet sites due to in-situ diffusion at 340℃. From 5 to 10 min, the oval discs changed into bigger hollow-discs on top of etched pits, accompanied by an anisotropical growth of the inner edge with110as the preferential orientation; moreover, the average height in110 was found to be the highest, indicating the preferential diffusion, accumulation and growth of Ga. From 10 to 12. 5 min, only the etched pits existed.Possible Ga-droplet etching mechanism was proposed.