8.7 W/mm output power density and 42% power-added-efficiency at 30 GHz for AlGaN/GaN HEMTs using Si-rich SiN passivation interlayer

In this work, high-performance millimeter-wave AlGaN/GaN structures for high-electron-mobility transistors (HEMTs) are presented using a Si-rich SiN passivation layer. The analysis of transient and x-ray photoelectron spectroscopy measurements revealed that the presence of the Si-rich SiN layer leads to a decrease in the deep-level surface traps by mitigating the formation of Ga-O bonds. This results in a suppressed current collapse from 11% to 5% as well as a decreased knee voltage (V-knee). The current gain cutoff frequency and the maximum oscillation frequency of the devices with the Si-rich SiN layer exhibit the values of 74 and 140 GHz, respectively. Moreover, load-pull measurements at 30 GHz show that the devices containing the Si-rich SiN deliver excellent output power density of 8.7 W/mm at V-ds = 28 V and high power-added efficiency up to 48% at V-ds = 10 V. The enhanced power performance of HEMTs using Si-rich SiN interlayer passivation is attributed to the reduced V-knee, the suppressed current collapse, and the improved drain current.