Hot-Electron-Induced Degradation in BCB- and SiN-Passivated $\hbox {Al}_{0.25}\hbox {Ga}_{0.75}\hbox {As/In}_{0.2}\hbox {Ga}_{0.8}\hbox {As}$ PHEMTs

In this paper, the hot-electron-induced degradation in Al_0.25Ga_0.75As/In_0.2Ga_0.8As pseudomorphic high-electron-mobility transistors passivated by low-k benzocyclobutene (BCB) has been investigated. Compared to the more commonly used silicon nitride (SiN), BCB has a lower dielectric constant and loss tangent and is becoming popular for passivation. However, its influence on the device hot-electron reliability has not been extensively studied so far. This paper examines the changes in the device dc drain-current, transconductance, and OFF-state breakdown voltages before and after hot-electron stress. For comparison purposes, the results for a device passivated using SiN have been included. The dominant mechanism that is responsible for the degradation in each technology has also been proposed and explained.