Low Damage, Cl₂-Based Gate Recess Etching for 0.3-μm Gate-Length AlGaN/GaN HEMT Fabrication

The traditional dry etching for GaN using the Ar/Cl₂ mixture gas in the reactive ion etching system has been developed. In order to reduce the surface damage, the additional CH₄ gas is introduced. However, this approach still has the problems of the residual surface damage and low etching selectivity between the AlGaN and GaN materials. Therefore, the following rapid thermal annealing (RTA) at 700°C is necessary to recover the surface properties. In this study, we proposed the Ar/Cl₂/CH ₄/O₂ for the GaN gate-recess etching in AlGaN/GaN HEMTs fabrication, which achieves a low surface damage and a high etching selectivity simultaneously. The 0.3 μm gate-length AlGaN/GaN HEMTs present a transconductance of 230 mS/mm, an f_Tr of 48 GHz, and f_max of 60 GHz, respectively.