Abstract This work presents a detailed TCAD and TRIM-based simulation study of normally-off AlGaN/GaN high-electron-mobility transistors (HEMTs), focusing on the influence of GaN cap layer thickness on device performance. The study evaluates threshold voltage modulation through nitrogen ion implantation across cap thicknesses of 0 nm, 1 nm, and 2 nm. The 2 nm cap configuration yielded optimal results, including a breakdown voltage of 720 V, drain current density of 1.45×10⁻² A/mm, gate leakage current of 5.35×10⁻¹¹ A/mm, and a positive threshold voltage of 0.366 V. TRIM simulations confirmed that the cap layer significantly affects nitrogen ion distribution and damage profiles, influencing 2DEG formation. Schottky barrier height variations were also observed, correlating with cap-induced modulation of surface potential. The simulated device achieved a power conversion efficiency of 98.2% in a 1 MHz buck converter circuit. These results demonstrate the effectiveness of GaN cap layer engineering in enhancing breakdown strength, gate control, and energy efficiency in E-mode GaN HEMTs.
Reddy et al. (Tue,) studied this question.