Low-Pressure-Chemical-Vapor-Deposition SiNx passivated AlGaN/GaN HEMTs for power amplifier application

A Low-Pressure-Chemical-Vapor-Deposition (LPCVD) bilayer SiN_x passivation scheme has been investigated and developed, which effectively suppress the current collapse in AlGaN/GaN HEMTs. Low current slump is very helpful for microwave power amplifier application. Compared to in-situ SiN_x passivations by metal-organic-chemical-vapor-deposition (MOCVD) and ex-situ SiN_x passivations by plasma-enhanced-chemical-vapor-deposition (PECVD), the LPCVD SiN_x exhibits the quickest recovery time from double-sweep IV curves. From pulsed IV and load-pull measurements, LPCVD SiN_x is also confirmed to deliver superior large signal performance. The bilayer LPCVD SiN_x passivated device shows negligible current slump (<;6%). These characteristics are directly reflected in the large signal operation, where HEMTs with bilayer LPCVD SiN_x have highest output power (2.9 W/mm at 3 GHz).