InAs quantum dot clusters grown on GaAs droplet templates: surface morphologies and optical properties.

GaAs nano-mounds formed by droplet epitaxy are used as templates for growth of self-assembled InAs quantum dot clusters (QDCs). These QDCs are found to contain an average of thirteen dots per cluster, of which there are two families of different sized quantum dots. Excitation intensity-dependent photoluminescence (PL) demonstrates that there is no lateral coupling between the two different size quantum dots. Lateral transfer of carriers is observed between different size quantum dots due to thermal activation as seen in their different temperature-dependent optical behaviors.

Composite droplets: evolution of InGa and AlGa alloys on GaAs(100).

We present a comparative study for the evolution of utilizing indium gallium (InGa) and aluminum gallium (AlGa) alloys fabricated on GaAs(100) by means of simultaneous and sequential droplet formation. The composite alloys reported using the sequential approach lack the ability to precisely determine the final alloy composition as well as consistency in the density of the droplets. Further, the composition of the InGa alloy is not uniform, as seen by the size distribution using an atomic force microscope (AFM). Although this approach may be acceptable for materials with similar surface kinetics, as in the case of AlGa, it is not acceptable for InGa. This investigation reveals that the simultaneous approach for fabricating composite alloys is the optimum approach for producing InGa alloys with better control on composition for plasmonic applications such as plasmonic waveguides.

Structural Evolution During Formation and Filling of Self-patterned Nanoholes on GaAs (100) Surfaces.

Nanohole formation on an AlAs/GaAs superlattice gives insight to both the "drilling" effect of Ga droplets on AlAs as compared to GaAs and the hole-filling process. The shape and depth of the nanoholes formed on GaAs (100) substrates has been studied by the cross-section transmission electron microscopy. The Ga droplets "drill" through the AlAs layer at a much slower rate than through GaAs due to differences in activation energy. Refill of the nanohole results in elongated GaAs mounds along the [01-1] direction. As a result of capillarity-induced diffusion, GaAs favors growth inside the nanoholes, which provides the possibility to fabricate GaAs and AlAs nanostructures.