Anomalous formation of InGaN/GaN multiple-quantum-well nanopillar arrays by focused ion beam milling

A GaN swelling-milling competition phenomenon was found under focused ion beam milling. Tuning the beam dwell time or introducing dopants into GaN is able to control the degree of GaN swelling, which makes feasible the writing of large-area nanopillar arrays. High-aspect-ratio InGaN/GaN MQW nanopillars were accordingly fabricated by a self-masking process where the tops of the p-GaN tips were swollen during milling. The shadowing effect from the swollen tops induced only minimal damage to the MQWs, with the cathodoluminescence (CL) emission peak of the InGaN/GaN MQWs showing a blue shift of about 35 meV compared with that of the as-grown wafer