Structural and optical properties of nanodots, nanowires, and multi-quantum wells of III-nitride grown by MOVPE nano-selective area growth

Abstract : Nanodots, nanowires, and semi-polar quantum well structures of GaN-based material have been grown by nano-selective area growth (NSAG). The growth evolution of the nanostructure has been studied. Cross-sectional transmission electron microscopy (TEM) shows that the nanostructures are free of threading dislocations. The growth of AlGaN/GaN layers is uniform and shows sharp interfaces between the AlGaN and GaN epilayers. AlGaN nanodots/nanowires, which are formed at the apexes of the nano-pyramids/nano-ridges, are found to be homogeneous in size and to have a higher aluminum mole fraction than the surrounding material. In contrast, the InGaN/GaN growth shows no quantum dots at the apexes of the nanostructures. We found that the growth facets of different Miller’s indices are formed on the InGaN/GaN nano-ridges. Energy dispersive X-ray spectroscopy (EDX) shows higher indium incorporation at the intersection of the growth facets. Cathodoluminescence measurements show enhanced luminescence intensity from InGaN multi-quantum wells (MQWs) grown on the nanostructure compared to that from InGaN MQWs grown on an unpatterned area.