Atomic-layer etching of GaN by using an HBr neutral beam

In the gate-recess formation process, normally-off operation is achieved by removing the barrier layer by dry etching to reduce the two-dimensional-electron-gas concentration under the gate electrode. An atomic-layer defect-free etching of GaN is thus indispensable to achieve high-frequency, high-power, and normally-off operation. More-precise atomic-layer defect-free GaN etching was investigated by using an HBr neutral beam. This investigation found that the HBr neutral beam could achieve more-precise atomic-layer etching than the Cl₂ neutral beam because the HBr chemistry can control the reactivity of atomic-layer etching by forming a thinner and less-volatile reaction layer.