Device Optimization of T-shaped Gate and Polarized Doped Buffer-Engineered InAlN/GaN HEMT for Improved RF/Microwave Performance.

III-nitride high-electron-mobility transistors (HEMTs) are the optimal choices for high-RF and power applications due to their exceptional performance characteristics. Nevertheless, HEMTs face formidable challenges related to large gate and buffer leakage currents, which inevitably impose significant limitations on device performance and reliability. In response to these challenges, this work studies the design consideration of a T-shaped gate InAlN/AlN with polarized doped buffer HEMT. The simulation results show that the parasitic capacitances are deeply affected by the geometry of the T-gate. The less influence of gate-to-source capacitance (Cgs) by the drain voltage possesses constant depletion charges at the source side, leading to a persistent value of Cgs with drain bias. Moreover, a polarization-doped buffer layer has been incorporated, effectively enhancing the confinement of the two-dimensional electron gas by causing an upward convex bend in the conduction band. This strategic design element significantly contributes to the reduction in leakage current (10−8), positive shift of Vth (0.9 V), and improves the switching ratio (108). The effect of gate head length (Hlength), gate stem height (Sheight), and gate foot length (Flength) on various RF parameters has been investigated. The simulated results confirm that the proper choice of Hlength (280 nm), Sheight (100 nm), and Flength (10 nm) significantly reduced the parasitic capacitance (Cgs = 350 fF/mm and Cgd = 140 fF/mm) and enhanced the Fmax (840 GHz), GBP (636 GHz), Ft (583 GHz) and also improved the power gains. The extracted results of the proposed design exhibit its efficacy for high-performance RF/microwave applications. [ABSTRACT FROM AUTHOR]