Effect of defects in oxide templates on Non-catalytic growth of GaN nanowires for high-efficiency light-emitting diodes

Abstract

Two kinds of oxide templates, one with and one without undercuts, are employed to study the effect of defects in oxide templates on non-catalytic growth of GaN nanowires (NWs). GaN NWs abnormally grown from the templates containing undercuts exhibit two types of patterns: earlystage growth of premature NWs and abnormally-overgrown (~2 μm) NWs. GaN NWs grown on perfectly-symmetric template patterns are highly crystalline and have high aspect ratios (2 ~ 5), and their tops are shaped as pyramids with semipolar facets, clearly indicating hexagonal symmetry. The internal quantum efficiency of the well-grown NWs is 10% larger than that of the deformed NWs, as estimated by using photoluminescence. These results suggest that our technique is an effective approach for growing large-area-patterned, vertically-aligned, hexagonal GaN NWs without catalysts, in strong contrast to catalytic vapor-liquid-solid growth, and that good formation of the oxide templates is crucial for the growth of high-quality GaN NWs.