Surface modification on GaAs by in-situ pulsed UV laser

A single-beam of UV pulse laser (355nm/10ns) was used to irradiate the as-grown GaAs (100) surface in-situ in molecular beam epitaxy with pulse numbers from 1 to 6 at laser intensity of 52.5 mJ/cm2/pulse. It was observed that the irradiated GaAs surface morphology depended strongly on the pulse number. For single pulse irradiation, small nano-dots (NDs) with high density were produced on the surface. The size of NDs increased and nano-rings (NRs) were observed with the increasing of pulse numbers. The surface was completely dominated by NRs at 6 pulses of laser irradiating. Arsenic atoms were selectively desorbed away from GaAs surface by laser irradiation leaving plenty of naked Ga-atoms to form small metal-dots of Gallium. Ga-rich NDs transferred to Ga droplets with the increased number of the laser pulses. NRs formed just as the traditional droplet-epitaxy process when the droplet size grew up to a critical size. Nano-drill process played an important role in the process. This research was supposed to provide a novel and promising solution for more controllable nano-fabrication of various semiconductor materials of MBE growing, including but not limited to GaAs reported here.