Comparison of Recessed Gate-Head Structures on Normally-Off AlGaN/GaN High-Electron-Mobility Transistor Performance

In this work, different gate-head structures have been compared in the context of AlGaN/GaN-based high-electron-mobility transistors (HEMTs). Field-plate (FP) technology self-aligned to the gate electrode leads to various gate-head structures, most likely gamma (Gamma)-gate, camel (-)-gate, and mushroom-shaped (T)-gate. In-depth comparison of recessed gate-head structures demonstrated that key performance metrics such as transconductance, output current, and breakdown voltage are better with the T-gate head structure. The recessed T-gate with its one arm toward the source side not only reduces the source-access resistance (R-g + R-gs), but also minimizes the source-side dispersion and current leakage, resulting in high transconductance (G(m)) and output current (I-DS). At the same time, the other arm toward the drain-side reduces the drain-side dispersion and tends to distribute electric field peaks uniformly, resulting in high breakdown voltage (V-BR). DC and RF analysis showed that the recessed T-gate FP-HEMT is a suitable candidate not only for high-frequency operation, but also for high-power applications.