Cl2/Ar based atomic layer etching of AlGaN layers

Abstract

This paper reports on atomic layer etching of several III-N materials such as GaN, AlN, AlGaN, and InAlGaN based on a sequential surface modification by chlorine adsorption followed by a low energy Ar plasma exposure to remove the modified layer using a reactive ion etching system. A study on the influence of several parameters, such as gas flow rates, removal step duration, RIE power and number of cycles on the etch per cycle, and the root-mean-square roughness, is performed. Low etch per cycle from 0.17 to 1.85 nm/cycle, respectively, for AlGaN and GaN and surfaces as smooth as the as-grown samples were obtained. The developed process is intended to be used for normally off GaN-based high electron mobility transistor processing.