Oxygen-based digital etching of AlGaN/GaN structures with AlN as etch-stop layers

TL;DR

This study demonstrates a precise oxygen-based digital etching process for AlGaN/GaN structures using AlN as an etch-stop layer, achieving controlled etch depths with minimal surface damage for device fabrication.

Contribution

The paper introduces a novel oxygen plasma digital etching method with AlN as an effective etch-stop layer for AlGaN/GaN structures, enabling precise control and reduced damage.

Findings

Etch depth of 5.7 nm per cycle at specific conditions

AlN layer effectively stops etching after 3 cycles

Surface roughness improved to 0.33 nm after 7 cycles

Abstract

O2-plamsa-based digital etching of Al0.25Ga0.75N with a 0.8 nm AlN spacer on GaN was investigated. At 40 W RF bias power and 40 sccm oxygen flow, the etch depth of Al0.25Ga0.75N was 5.7 nm per cycle. The 0.8 nm AlN spacer layer acted as an etch-stop layer in 3 cycles. The surface roughness improved to 0.33 nm after 7 digital etch cycles. Compared to the dry etch only approach, this technique causes less damages. It was shown to be effective in precisely controlling the AlGaN etch depth required for recessed-AlGaN HEMTs.