Improved Linearity of GaN HEMT Based on Three-Dimensional Gate Modulation Optimization

In this paper, the MIS-Fin structure is formed by adding SiN between Schottky-gate and AlGaN barrier to weaken the top gate control ability and improve the linearity of the device. The two-dimensional electron gas (2DEG) concentration distribution of planar HEMT, Fin HEMT, side gate HEMT, and MIS-Fin HEMT are studied for the first time. By comparing the distribution of 2DEG at different gate voltages, it was found that the MIS-Fin HEMT retains some top gate control capability while exhibiting gradual turn off of side gate. In order to better investigate the effect of Fin width on MIS-Fin HEMT linearity, the DC and small signal characteristics of the MIS-Fin HEMT were simulated at Fin widths of 100 nm, 200 nm, 300 nm, 400 nm, and 500 nm. The simulation found that the gate voltage swing (GVS) of the transconductance <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$(\mathrm{G}_{\mathrm{m}})$</tex> of the MIS-Fin HEMT was 4.8 V and the GVS of the current gain cutoff frequency <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$(\mathrm{f}_{\mathrm{T}})$</tex> was 6 V at Fin width of 500 nm. Through the above simulation, it was found that MIS-Fin HEMT have better linearity compared to other devices.