TiO2 insertion layer deposited before passivation to reduce etch damage on AlGaN/GaN HEMT

Gamma-gate has been used to increase the breakdown voltage of radio frequency (RF) devices, and the damage caused by gate pin etching has been studied. In this study, a TiO2 layer, acting as a protective layer, was inserted between the AlGaN barrier layer and SiN passivation layer. The AlGaN/GaN high-electron-mobility transistor (HEMT) with TiO2 had no kink effect in its output characteristic, and at high gate voltages, it demonstrated a higher transconductance than the HEMT without TiO2. The HEMT without TiO2 exhibited a more prominent saturation tendency for drain current. Additionally, the C-V test data show that the trap state density of the AlGaN/GaN interface of an AlGaN/GaN HEMT with TiO2 decreased compared with a HEMT without TiO2. DC and C-V test results show that the TiO2 layer can effectively reduce the etching damage of the material under the gate. (C) 2022 The Japan Society of Applied Physics