Removal of GaN film over AlGaN with inductively coupled BCl₃/Ar atomic layer etch

Abstract

In this work, atomic layer etching (ALE) of thin film GaN (0001) is reported in detail using sequential surface modification by BCl3 adsorption and removal of the modified surface layer by low energy Ar plasma exposure in a reactive ion etching system. The estimated etching rates of GaN were ~0.74 nm/cycle. The GaN was removed over AlGaN after 135 cycles. To study the mechanism of the etch, detailed characterization and analyses were carried out, including scanning electron microscope (SEM), X-ray photoelectron spectroscopy (XPS) and atomic force microscope (AFM). It was found that in the presence of GaClx after surface modification by BCl3, the GaClx was disappeared after low energy Ar plasma exposure, which effectively ed the mechanism of atomic layer etch. This technique enables a uniform and reproducible fabrication process for enhancement-mode high electron mobility transistors with a p-GaN gate.