Optimization of source-connected field plate in AlGaN/GaN HEMTs for high-performance and high-reliability operation: A simulation study

This study investigates the operational characteristics of AlGaN/GaN high-electron-mobility transistors (HEMTs) by systematically varying the top source-connected field plate length (L_TSFP), which controls the overall source-connected field plate configuration. The simulation parameters are calibrated to measured data from fabricated 0.15 μm planar-gate AlGaN/GaN HEMTs with a source-connected field plate to maintain simulation reliability. The simulations identify the field plate configuration that co-optimizes DC, RF, and dynamic performances for L_TSFP between 0.1 μm and the conventional 1.4 μm. The results demonstrate that an increase in L_TSFP from 0.1 μm to 0.5 μm yields an approximately 9.34 % improvement in breakdown voltage (V_BD); however, further increases beyond 0.5 μm show saturation with no significant enhancement. Additionally, the gate-to-source capacitance displays a significant decrease as L_TSFP scales down from 1.4 μm to 0.5 μm, and it then reaches a plateau for further scaling to 0.1 μm. The cut-off frequency (f_T) converges to approximately 46.23 GHz for L_TSFP below 0.5 μm. As a result, the device with L_TSFP of 0.5 μm achieves the highest Johnson's figure of merit (=V_BD×f_T) of 5.31 THz-V, representing a 28.29 % improvement over the conventional 1.4 μm configuration. Moreover, the dynamic performance metrics, characterized by the suppressed current collapse and reduced normalized on-resistance, show only marginal improvement for L_TSFP values above 0.5 μm, which illustrates the limited benefit of further field plate extension in this regime. These findings indicate that AlGaN/GaN HEMTs with an optimized L_TSFP effectively balance high-power, high-frequency, and reliable operations, making them promising candidates for advanced power electronics and RF applications.