Selective Area Growth (SAG) by Molecular Beam Epitaxy (MBE) is one of the best approaches to develop a variety of nanostructures on different substrates. Ordered axial InGaN/GaN nanoLED structures were grown on GaN/sapphire templates as well as on GaN buffered Si(111) substrates. Core-shell InGaN/GaN microstructures can also be grown following two approaches: i) from top–down (etched) GaN cores and ii) from bottom-up GaN cores. In both cases a subsequent conformal growth of InGaN layers was achieved. Based on this approach, core-shell nanoLED arrays were successfully fabricated.
A basic aspect of SAG refers to the initial stages of nanocrystals nucleation within the nanoholes that lead to their stable hexagonal structure and the efficient filtering of dislocations coming from the substrate, strongly dependent on the nano/microrod geometry.
A common observed feature is that In incorporation depends strongly on the crystal plane considered, either m- or r-plane, giving rise to two InGaN related emissions. Exploiting this effect, dot-in-a-wire InGaN structures were grown embedded in ordered GaN nanorods acting as Single Photon Emitters.
Nano/microrods can also be used as nanoFET transistors with a semi-cylindrical gate direct contact allowing for a very tight electrostatic control of the channel.
SAG is also used to grow ordered nanostructures on semi-polar and non-polar orientations GaN/sapphire templates with the aim to fabricate ternary pseudo-substrates with tailored lattice constant and very high crystal quality.
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