Optical spectroscopic studies of InAs layer transformation on GaAs surfaces

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Abstract
The optical properties of InAs monolayer and submonolayer coverage formed in a GaAs matrix by molecular-beam epitaxy have been studied. Prolonged growth interruptions were introduced after the InAs layer was deposited. In samples with intentionally deposited submonolayer InAs coverage, the luminescence efficiency was maintained and no emission line broadening was observed up to very long interruption times, suggesting this arrangement is stable. On the other hand, one InAs ML was found to be unstable with a tendency towards transformation into two surface arrangements: InAs anisotropic multilayer islands and uniform submonolayer distribution of InAs molecules over the surface. For InAs coverage larger than 1 ML, it was found that long growth-interruption times favor the formation of thicker three-dimensional InAs islands and may result in a local strain relief. It was found that in the case of monolayer coverage, the luminescence line shape broadens and the intensity decreases as the growth interruption time increases. Our results explain how the marked improvement of the optical quality of structures grown by submonolayer epitaxy may arise.