Thickness-Dependent AlGaN Back Barrier Solutions for Short-Channel Effect Mitigation in T-gate AlGaN/GaN HEMTs

This work presents a comprehensive analysis of the DC and RF characteristics of T-gate (0.25 μm) AlGaN/GaN high-electron-mobility transistors (HEMTs) by incorporating AlGaN back barriers with thicknesses of 50 and 15 nm into the epitaxial structure. The inclusion of the 50 nm AlGaN back barrier significantly enhanced the DC performance, achieving a high on/off current ratio of 1.5 × 10⁴, two orders of magnitude greater than that of the device employing a thinner 15 nm barrier. This improvement is due to a reduced drain-induced barrier lowering (DIBL) of 68 mV V⁻¹, compared to 72 mV V⁻¹ for the 15 nm AlGaN back barrier, highlighting the 50 nm back barrier effectiveness in mitigating short-channel effects. Additionally, the thicker back barrier effectively suppresses vertical carrier penetration, thereby lowering carrier trapping in the buffer layer and enhancing drain lag performance. The RF characteristics also showed notable performance, with small-signal and large-signal parameters demonstrating a cut-off frequency (F_T) of 59 GHz, a maximum oscillation frequency (F_MAX) of 138 GHz, a power-added efficiency (PAE) of 16.75%, and an output power (P_out) of 21.55 dBm at 28 GHz.