A Novel Oxygen-Based Digital Etching Technique for p-GaN/AlGaN Structures without Etch-Stop Layers**Supported by the Guangdong Science and Technology Department (Grant Nos. 2019B010128001 and 2019B010142001), the Shenzhen Municipal Council of Science and Innovation (Grant Nos. JCYJ20180305180619573 and JCYJ20170412153356899), and the National Natural Science Foundation of China (Grant No. 61704004).

Abstract

A novel O2 plasma-based digital etching technology for p-GaN/AlGaN structures without any etch-stop layer was investigated using an inductively coupled plasma (ICP) etcher, with 100 W ICP power and 40 W rf bias power. Under 40 sccm O2 flow and 3 min oxidation time, the p-GaN etch depth was 3.62 nm per circle. The surface roughness improved from 0.499 to 0.452 nm after digital etching, meaning that no observable damages were caused by this process. Compared to the dry etch only methods with Cl2/Ar/O2 or BCl3/SF6 plasma, this technique smoothed the surface and could efficiently control the etch depth due to its self-limiting characteristic. Furthermore, compared to other digital etching processes with an etch-stop layer, this approach was performed using ICP etcher and less demanding on the epitaxial growth. It was proved to be effective in precisely controlling p-GaN etch depth and surface damages required for high performance p-GaN gate high electron mobility transistors.