Passivation Effects of 100 nm In0.4AlAs/In0.35GaAs Metamorphic High-Electron-Mobility Transistors with a Silicon Nitride Layer by Remote Plasma-Enhanced Chemical Vapor Deposition

Abstract

In0.4AlAs/In0.35GaAs metamorphic high-electron-mobility transistors (MHEMTs) have been successfully fabricated. In order to reduce the surface effects on the barrier layer, Si3N4 layer passivation by remote plasma-enhanced chemical vapor deposition (PECVD) is utilized, which might suppress the surface trap density in side-recessed region and reduce the parasitic resistance. The device simulation was performed to derive the effects of surface trap in the side-recessed region. As the surface trap density decreases, ID.max increases because of the stabilization of the surface states in the side-recessed region. This result indicates that the increases of gm.max and ID.max are related with both the reduction of parasitic resistance and the gate-sinking effect. The fabricated 100 nm MHEMTs with the passivated of Si3N4 layer exhibited excellent characteristics such as a maximum extrinsic gm.max of 740 mS/mm and a cut off frequency ( fT) of 210 GHz.