Influence on Noise Performance of GaN HEMTs With In Situ and Low-Pressure-Chemical-Vapor-Deposition SiNx Passivation

High-frequency and low-frequency noise (LFN) performance of GaN high electron-mobility transistors (HEMTs), passivated with SiNx deposited by either in situ or low-pressure-chemical-vapor-deposition (LPCVD), are compared. From 8-26 GHz, the LPCVD sample has a lower minimum noise figure (1 dB at 8 GHz) because of lower power spectral density of noise sources and less transconductance (gm) dispersion. The LPCVD and the in situ SiNx passivated HEMTs exhibit similar LFN in the 1 Hz-100 kHz range (drain current noise spectra~10
^-17
A
²
/Hz at 100 kHz). Nevertheless, LPCVD should be a preferred choice for voltage-controlled oscillator (VCO) applications, since it is capable of suppressing current collapse more effectively, which results in a higher output power and, therefore, a lower phase noise. Furthermore, the low current collapse, low LFN, and minimum noise figure makes the LPCVD SiNx passivation a promising candidate for multifunctional monolithic microwave integrated circuits, including power amplifiers, low-noise amplifier, switches, mixers, and VCOs.