Investigation of plasma etch damage in GaN on commercially available substrates by Raman spectroscopy

Abstract

In this work, we evaluate the quality of a commercially available GaN/AlGaN structure grown on Qromis Substrate Technology using Raman spectroscopy. Using the shift of the E2H peak, we calculated that initially this GaN structure has a lower biaxial stress than commercially available GaN on sapphire. After Cl2/Ar based reactive ion etching, surface damage was evident by an 80% stress increase. However, the implementation of wet alkaline etch treatments using potassium hydroxide and tetramethyl ammonium hydroxide (TMAH) relieved the stress by equal amounts. While these results indicate equivalent recovery between treatments, devices fabricated with a TMAH treatment exhibit superior electrical behavior.