Simulation-Based DC and RF Performance Analysis of an Enhancement-Mode T-Gate Al_0.15Ga_0.85N/GaN/Al_0.07Ga_0.93N/GaN/Al_0.05Ga_0.95N MIS-HEMT Device on a GaN Substrate

This paper presents a metal–insulator–semiconductor high-electron-mobility transistor (MIS-HEMT) device, operating in enhancement mode, with a double-channel triple-barrier (DCTB) Al_0.15Ga_0.85N/GaN/Al_0.07Ga_0.93N/GaN/Al_0.05Ga_0.95N device structure. Initially, we simulate the Al_0.15Ga_0.85N/GaN single-channel single-barrier (SCSB) MIS-HEMT, featuring a T-gate design that offers a significant gap between the gate and a drain electrode, resulting in a high breakdown voltage (V_BD) and low parasitic capacitance, enhancing cut-off frequency (f_t) and a maximum frequency of oscillation (f_max). In the current era, high breakdown voltage, high current drive, and high-frequency enhancement-mode-operated devices are needed for power switching circuits and high-frequency power amplifier applications. To meet these requirements, we propose a DCTB MIS-HEMT device structure that adds additional back-barrier layers and channel layers to form a double-hump characteristic due to the interaction between two-dimensional electron gas (2DEG) accumulation layers and the electric field across the device. We optimize the devices with an optimistic doping profile in channel and buffer layers, a field plate, recessed gate structure, and control the barrier layers thickness, ensuring enhancement-mode operation. Numerical simulations of the DCTB device provide high drain current (I_ds) of 1.5 A/mm, transconductance (g_m) of 0.232 S/mm, threshold voltage (V_t) of 2.8 V, V_BD of 633.1 V, ON resistance (R_ON) of 6.074 Ω mm, f_t of 49.8 GHz, and f_max of 107.8 GHz. Due to improvements in these parameters, the DCTB MIS-HEMT outperforms the SCSB MIS-HEMT, making it suitable for high-current drive, high-frequency, and high-speed switching applications. In this work, we also examine the merits of utilizing DCTB MIS-HEMT as the switching element in an ultra-low-loss boost converter circuit.