The AFM study of a series of novel nano-structure on in-situ laser irradiating GaAs(001) substrate in molecular beam epitaxy was presented. Nano-hole, nano-island and nano-ring(Chinese ancient copper coin shape) were observed after laser irradiating. The desorption of Gallium on GaAs surface varies according to different power energy and pulse numbers, leading to the formation of nano-holes, nano-islands and nano-rings. It is speculated that these nanostructures are galliumrich through the change of the RHEED stripe. What’s more, the desorption of defectless GaAs sub-monolayer was discovered, and matched dynamic evolution model (self-drilling effect dominated by Ga atom) was presented. The dependence of the temperature on the surface of the substrate with time was studied after laser irradiating according to the heat conduction equation. The drastic temperature changes caused non-thermodynamic equilibrium process which makes these morphologies.
In this work, surface modification of InAs wetting layer was carried out during InAs/GaAs (001) quantum dot molecular beam epitaxy growth by in-situ pulsed laser (355 nm/ 10 ns). We investigated the morphology transformation of wetting layer by atomic force microscope. Atomic layer removal and formation of nano holes were observed on the sample surface. It is proposed that the material removal of wetting layer induced by electronic excitation is triggered by In atom vacancies due to the desorption at substrate temperature of 480°C. The effects of surface modification on QD growth were studied by subsequent InAs deposition after laser irradiation. Preferential nucleation in nano holes were found in the experiments. This study provides a novel technique leading to site-controlled to InAs/GaAs (001) QDs fabrication.