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

摘要

A bilayer SiN 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 SiN passivations by metal-organic chemical vapor deposition (MOCVD) and SiN 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 MOCVD SiN or PECVD SiN exhibit significant current slump (% and knee-voltage walkout, while the bilayer LPCVD SiN passivated device shows negligible current slump (% and knee-voltage walkout. These characteristics are directly reflected in the large signal operation, where HEMTs with bilayer LPCVD SiN have the lowest dynamic ON-state resistance and highest output power (5.4 W/mm at 3 GHz).