Suppression of Dispersive Effects in AlGaN/GaN High-Electron-Mobility Transistors Using Bilayer SiNx Grown by Low Pressure Chemical Vapor Deposition

Journal article, 2015

A bilayer SiNx passivation scheme has been developed using low pressure chemical vapor deposition (LPCVD), which effectively suppresses the dispersive effects in AlGaN/GaN high-electron-mobility transistors (HEMTs) for microwave power operation. The bilayer LPCVD passivation is compared with in-situ SiNx passivations by metal-organic chemical vapor deposition (MOCVD) and ex-situ SiNx passivations by plasma-enhanced chemical vapor deposition (PECVD). The HEMTs were fabricated and characterized in terms of pulsed IV, transient drain current, and load pull. The devices passivated with in-situ MOCVD SiNx or PECVD SiNx exhibit significant current slump (similar to 40%) and knee-voltage walkout, while the bilayer LPCVD SiNx passivated device shows negligible current slump (similar to 6%) and knee-voltage walkout. These characteristics are directly reflected in the large signal operation, where HEMTs with bilayer LPCVD SiNx have the lowest dynamic ON-state resistance and highest output power (5.4 W/mm at 3 GHz).