Site-controlled growth of indium nitride based nanostructures using metalorganic vapour phase epitaxy

In this paper we report on studies on how to obtain selective area growth of indium nitride nanostructures on patterned SiO2/GaN(0 0 0 1)/c-plane α-Alα-Al2O3 substrates by means of metalorganic vapour phase epitaxy (MOVPE) for very small pattern filling factors. To this end we investigated the impact of growth parameters such as substrate temperature and the group V/group III molar flow ratio (V/III ratio) on nanostructure morphology and on selectivity. Furthermore we examined the evolution of InN nanostructure growth in 100 nm apertures and the influence of growth stage on the nanostructure's optical characteristics. We found a narrow growth parameter range in which both the reproducible selective growth of InN inside the circular apertures and the parasitic nucleation on the mask were concurrently kept under control. Under these optimized growth conditions we obtained regular, hexagonally shaped nanopyramids which evolved from coalesced nucleation seeds via cauldron-like structures. A systematic study of the nanostructure evolution reveals that the near band edge luminescence depends on the nanostructure growth stage, which is assigned to different strain states and to defect induced free carriers as the InN nanopyramids grow