Reduction of Surface Roughness in Photoenhanced Electrochemical Wet‐Etched GaN

The roughness of GaN surfaces produced by photoenhanced etching is significantly reduced by the introduction of an external bias voltage during the etching process. The root‐mean‐square surface roughness decreases from a maximum of approximately 1700 nm to a minimum of 20 nm as the bias voltage is increased from 0 to 2.5 V, and as the KOH concentration is decreased from 1.0 to 0.01 M. Etch rates as high as 0.4 μm/min are achieved at room temperature, producing surfaces with roughnesses of only 20 nm.