GaN nanostructures by reactive ion etching: Mask and Maskless approach

Abstract

GaN nanostructures have been fabricated by reactive ion etching (RIE) with and without mask. The mask comprising of self assembled nanoparticles has been prepared by rapid thermal annealing (RTA) of thin film of Ni deposited on GaN epilayers grown by Metal Organic Vapor Phase Epitaxy (MOVPE). Effect of RTA temperature and time on the morphology of mask has been studied using 5 and 10 nm thick Ni films. Using 5 nm Ni film, a good mask composed of sub 50 nm agglomerated nanoparticles in high density (>1E10 /cm2) was fabricated at 850 °C after 90–120 s of RTA. The samples were subjected to BCl3/Cl2 plasma based inductively coupled plasma RIE (ICP-RIE) process to fabricate the nanostructures. The morphology of the fabricated nanostructures exhibited direct correspondence to the Ni mask used. No etching was observed in material underneath the mask area. Conical nanostructures were fabricated in high density with diameter and height of 100 nm and 150 nm. The size of the nanoparticles was identified as the major limitation to fabricate high aspect one dimensional structures like nanowires using this approach. To overcome this limitation, a novel maskless RIE process has been employed with careful choice of process parameters and nanowires with sub 40 nm diameter and 280–300 nm height were successfully fabricated in high density (∼1E10 /cm2) using GaN epilayers with high dislocation density.