Improvement of DC Performance and RF Characteristics in GaN-Based HEMTs Using SiN_x Stress-Engineering Technique

In this work, the DC performance and RF characteristics of GaN-based high-electron-mobility transistors (HEMTs) using the SiN_x stress-engineered technique were systematically investigated. It was observed that a significant reduction in the peak electric field and an increase in the effective barrier thickness in the devices with compressive SiN_x passivation contributed to the suppression of Fowler-Nordheim (FN) tunneling. As a result, the gate leakage decreased by more than an order of magnitude, and the breakdown voltage (BV) increased from 44 V to 84 V. Moreover, benefiting from enhanced gate control capability, the devices with compressive stress SiN_x passivation showed improved peak transconductance from 315 mS/mm to 366 mS/mm, along with a higher cutoff frequency (f_t) and maximum oscillation frequency (f_max) of 21.15 GHz and 35.66 GHz, respectively. Due to its enhanced frequency performance and improved pinch-off characteristics, the power performance of the devices with compressive stress SiN_x passivation was markedly superior to that of the devices with stress-free SiN_x passivation. These results confirm the substantial potential of the SiN_x stress-engineered technique for high-frequency and high-output power applications, which are crucial for future communication systems.