STUDIES ON INTERSURFACE DIFFUSION IN NANO-STRUCTURE EPITAXY

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In the present study, the surface diffusion of Ga between two growing surfaces in molecular beam epitaxy (MBE) of GaAs was studied first. We call such diffusion as an inter-surface diffusion. The intersurface diffusion governs the growth of micro/nano structures and one of the key elementary growth processes which determine the appearing and disappearing of a certain facet. It turned out that the amount and the direction of the intersurface diffusion depends strongly on As pressure. It was found that the top size of a truncated pyramid or ridge can be controlled by changing arsenic pressure. For instance, the top of truncated pyramid is decreased during the growth at lower As pressure while it is increased under higher As pressure. By rotating the substrate, it was possible to get uniform truncated pyramids with controlled top size so that one can grow dot structures on the tops.In the next step, the order of reaction of AィイD2s2ィエD2 and AィイD2s4ィエD2 with Ga in MBE growth was studied. It was found that under a low As pressure the order was the first while under high As pressure it was the second for both As species. As for As4 the result shows good agreement with well known results reported by Foxon and Joyce while the presence of the second order reaction regime for AィイD2s2ィエD2 has not been reported.