Fabrication of high quality GaN nanopillar arrays by dry and wet chemical etching

TL;DR

This study investigates the fabrication of high-quality GaN nanopillar arrays using ICP dry etching and wet chemical treatments, focusing on optimizing surface quality and strain relaxation for improved nanostructure performance.

Contribution

It demonstrates how etching parameters and post-etch wet treatments can enhance GaN nanopillar quality by reducing surface damage and promoting strain relaxation.

Findings

Wet KOH etching removes plasma-induced surface damage.

Strain relaxation is confirmed via Raman spectroscopy.

Whispering gallery modes observed in photoluminescence.

Abstract

We study strain relaxation and surface damage of GaN nanopillar arrays fabricated using inductively coupled plasma (ICP) etching and post etch wet chemical treatment. We controlled the shape and surface damage of such nanopillar structures through selection of etching parameters. We compared different substrate temperatures and different chlorine-based etch chemistries to fabricate high quality GaN nanopillars. Room temperature photoluminescence and Raman scattering measurements were carried to study the presence of surface defect and strain relaxation on these nanostructures, respectively. We found that wet KOH etching can remove the side wall damages caused by dry plasma etching, leading to better quality of GaN nanopillars arrays. The Si material underneath the GaN pillars was removed by KOH wet etching, leaving behind a fine Si pillar to support the GaN structure. Substantial strain relaxations were observed in these structures from room temperature Raman spectroscopy measurements. Room temperature Photoluminescence spectroscopy shows the presence of whispering gallery modes from these the nano disks structures.