Electrochemical etching of p-type GaN using a tunnel junction for efficient hole injection

In this work electrochemical etching (ECE) of p-type GaN under constant bias without an external light source is demonstrated for the first time. A tunnel junction (TJ) was used as a cap to ensure stable and controllable hole injection to the p-type semiconductor. GaN and In0.02Ga0.98N layers with two different Mg dopant concentrations (5.6∙1018 and 2∙1019cm−3, respectively) were investigated. Structuring of the samples into double-step stripes allowed examination of the etching mechanism. The etch rate and threshold etching voltage were determined. Finally, a model of the band structure of the etched samples is presented. Based on experimental results and theoretical considerations this work provides a method for controllable ECE of p-type GaN using TJ for efficient hole injection.