A wet photochemical etching technique promises to ease the production of devices fabricated from GaN-based materials, which are resistant to most chemical etches and which can display defects when dry-etched. In the March 26 issue of Applied Physics Letters, researchers at the University of California in Santa Barbara describe how they produced 500-µm undercuts in InGaN/GaN heterostructures with the technique. The group immersed samples in a 2.2-mol KOH solution and exposed them to light from a 1-kW XeHg lamp through their sapphire substrate. The team reported lateral etch rates of up to 10 µm/min and used a lift-off process to remove the samples, which were mechanically polished to a roughness of 5.5 Å.