GaN-Based Junctionless Field-Effect Transistor with Hetero-Gate Dielectric for Enhancement of Direct Current and Radio Frequency Performance

In this paper, we propose a gallium nitride (GaN)-based junctionless field-effect transistor (JLFET) with a hetero-gate dielectric to enhance direct current (DC) and radio frequency (RF) performance. The heterogate dielectric structure composed of hafnium oxide (HfO2) and silicon dioxide (SiO2) increases an electron velocity in the channel region owing to an effective electric field distribution, and the rising electron velocity leads to the enhancement of transconductance (g(m)). The JLFET with hetero-gate dielectric structure also exhibited a high V-th with normally-off operation because the HfO2 in hetero-gate dielectric forms a high-energy barrier in source-side channel. The effects of the hetero-gate dielectric structure depend on device parameters including a doping concentration of GaN body (D-GaN), nanowire radius (R), and HfO2 length in the hetero-gate dielectric (L-HfO2). Moreover, the hetero-gate dielectric has great effect on gate capacitance (C-gg). The higher L-HfO2 causes the increase of C-gg. The JLFET with the optimum L-HfO2 of 20 nm obtains the improved cut-off frequency (f(T)) owing to a lower g(m)/C-gg ratio. The extracted results confirm the employment of hetero-gate dielectric structure simultaneously improve DC and RF performance of GaN-based JLFET.