Structure-related optical behavior of nanoscale GaN island, tip, tube and cone arrays formed by inductively coupled plasmas etching

We introduce a one-step self-assembled technique to form various nanostructures on N-type GaN film and then present an optical characterization of a series of low-dimensional GaN nanostructures by using low-temperature photoluminescence (LTPL) spectroscopy. Nanoscale GaN island, tip, tube and cone-like structures of diameters ranging from 50 to 190 nm were self-assembled on a c-axis perpendicular to substrate surface with uniform diameter and uniform length by inductively coupled plasmas etching process without lithography. Optical LTPL measurements on nanostructures show consistent variations in the properties of the fabricated GaN structures as a function of surface area of GaN nanostructures. LTPL mapping gives an evidence for defect-induced donors and/or acceptors near the facets of the ICP-etched nanostructure. Our results indicate that a higher concentration of donor-related defects is introduced on the surface of GaN nanotubes. In particular, the nanotubes sample exhibits a conspicuous increased in yellow luminescence intensity compared to the other nanostructure samples. This result may support more information for the application of nanotubes on nanogenerators.