Study on the modulation effect of gate etching depth on the electrical characteristics of AlGaN/GaN/AlN/GaN dual-channel devices

In this paper, multi-threshold HEMTs based on AlGaN / GaN / AlN / GaN structure are reported. By controlling the etching time of different gate trenches in the double channel, different gate trench depths are realized, and the gate control ability and the thickness of the barrier layer under the gate are changed, so as to adjust the threshold voltage. It is evident that by modifying the etching time of the gate slot, the threshold voltage can be adjusted from -5.8V to -0.2V. When the etching is set to 0s, 35s and 67s, good linearity is demonstrated, with the current gain cut-off frequency (fT) reaching up to 25 GHz and the maximum oscillation frequency (fmax) reaching 46 GHz. When the etching time is less than 100 s, the device can maintain good frequency characteristics and linearity. At a drain voltage of 20 V, the power added efficiency (PAE) of 56% and output power density (Pout) of 4.23 W/mm are achieved with the conventional T-gate. After trench etching to 67 s, the PAE is increased to 58%, while the Pout is reduced to 2.20 W/mm.