Inductively coupled plasma etching of GaN using Cl2/He gases

We investigated n-GaN etched by an inductively coupled plasma (ICP) etcher using Cl2/Ar and Cl2/He as the etching gases. A detailed study on the samples etched in different ICP power, RF power, process pressure and Cl2/Ar(He) mixing ratio was performed. It was found that n-GaN could be successfully etched by both Cl2/Ar and Cl2/He. The maximum etching rate could reach 8000 A min-1 for n-GaN etched in Cl2/Ar and 8400 A min-1 for n-GaN etched in Cl2/He. Furthermore, it was found that the specific contact resistance is 4.2x10-4 and 1.37x10-6 Ω-cm2 for n-GaN etched by Cl2/Ar and Cl2/He, respectively. The smaller contact resistance is probably due to the lighter He which induce smaller plasma damages during ICP etching