Self-termination of contactless photo-electrochemical (PEC) etching on aluminum gallium nitride/gallium nitride heterostructures

Abstract

Contactless photo-electrochemical (PEC) etching was successfully demonstrated on AlGaN/GaN heterostructures using a K2S2O8 aqueous solution. The etching was conducted by a simple method such as just dipping the sample with Ti-cathode pads into the solution under UVC illumination. The etching morphology of the AlGaN surface was very smooth with an root mean square roughness of 0.24 nm. The etching was self-terminated in the AlGaN layer, whose residual thickness was 5 nm uniformly throughout the etched region. These contactless PEC etching features are promising for the fabrication of recessed-gate AlGaN/GaN high-electron-mobility transistors with high recessed-gate thickness reproducibility.