Control of V th of the enhancement high-frequency AlGaN/GaN HEMT fabricated by oxygen-based digital etching

Abstract

We established an oxygen-based digital etching technique to fabricate the recessed gate structure for RF GaN HEMT. The digital etching rates were 2.5 nm cycle–1 and 0.5 nm cycle–1 with 40 W RF bias and 0 W RF bias for ICP oxidation, respectively. The roughness of the surface was around 0.1 nm. The V th of the recessed gate GaN HEMTs can be adjusted from D-mode to E-mode. The GaN HEMT with 110 nm gate length showed a maximum peak gm value of 440 mS mm−1 after 6 cycles of digital etching with V th near 0 V and ft values nearby 42 GHz.