31 W/mm at 8 GHz in InAlGaN/GaN HEMT With Thermal CVD SiNx Passivation

The study reports the findings on a quaternary InAlGaN/GaN high electron mobility transistor (HEMT) employing a thermal chemical vapor deposition (TCVD) silicon nitride (SiN _x ) passivation with a record high output power density of 31.0 W/mm in the X-band. We compared the two different SiN _x passivation methods, namely, TCVD deposition, and plasma-enhanced CVD (PECVD) deposition, for InAlGaN/GaN HEMTs and investigated the effects on device performance. PECVD SiN _x passivation caused a considerable degradation of the two-dimensional electron gas (2DEG) mobility. However, TCVD SiN _x could suppress the degradation of 2DEG mobility, resulting in a low sheet resistance of 293 ohm/sq. with a high 2DEG mobility of 2048 cm ² V ^-1 s ^-1 . Furthermore, InAlGaN/GaN HEMT with TCVD SiN _x passivation exhibited a high-drain current of 1230 mA/mm even after off-state stress due to the reduced current collapse and low sheet resistance. The off-state breakdown voltage increased from 169 to 227 V on using TCVD SiN _x despite an increase in the maximum drain current, resulting in a high voltage of 90 V at radiofrequency. We successfully demonstrated the state-of-the-art high output power density GaN-based HEMTs with an InAlGaN barrier and TCVD SiN _x passivation. Our results revealed that TCVD SiN _x passivation can facilitate the application of InAlGaN/GaN HEMTs for high-power amplifiers.