Optical investigation of micrometer and nanometer-size individual GaN pillars fabricated by reactive ion etching

We present an optical investigation of GaN pillars using both micro-Raman (μ-Raman) and microphotoluminescence (μ-PL) spectroscopy. GaN pillars of diameter ranging from 100 nm to 5 μm were fabricated by electron beam lithography and reactive ion etching (RIE) with ${\mathrm{SiCl}}_4$ plasma. Optical measurements of both μ-Raman and μ-PL on individual pillars show consistent variations in the properties of the fabricated GaN structures as a function of GaN pillar size. μ-PL mapping gives strong evidence for defect-induced donors and/or acceptors near the facets of the RIE etched pillars. RIE for the nanostructuration of GaN could be used in the future to allow spectroscopic studies of a few or single quantum objects such as GaN quantum dots.