Fabrication and characterization of GaN nanopillar arrays

Various nanofabrication technologies are currently under investigation to realize fine patterning of III-Nitrides. Dry and wet etching techniques have been explored in the past for the fabrication of GaN-based devices. However, due to etch-induced damage, it is still a major challenge to achieve high-quality GaN-based nanostructures with high aspect ratio. In this study, GaN nanopillars were fabricated by inductively coupled plasma etching (ICP) using anodic aluminium oxide (AAO) as a mask. High-spatial resolution optical techniques were employed to characterize these pillar arrays. The average diameter and length of these pillars are about 60-70 nm and 350-400 nm, respectively. Low temperature micro-photoluminescence spectra show a red shift compared with the spectrum recorded from the as-grown GaN, indicating stress relaxation in these nanopillars. The evidence of good crystalline quality is also confirmed by micro-Raman measurement where red shift of the E-2(TO) mode from GaN nanopillars suggest partial relaxation of the compressive strain.