Subthreshold characteristics of laterally gated AlGaAs/InGaAs pseudomorphic high-electron-mobility transistors fabricated with focused ion beam implantation

Abstract

We have used a focused ion beam (FIB) technique to fabricate laterally gated AlGaAs/InGaAs pseudomorphic high-electron-mobility transistors (pHEMTs), and have characterized them electrically. The FIB direct-write defines the current path. An ion dose of 1×10 14 ions cm −2 from a 25 keV Ga + beam gives satisfactory electrical isolation. The fabricated transistors show typical field-effect transistor (FET) characteristics. For a properly adjusted n-AlGaAs layer, transfer characteristics ( I ds vs. V g) in the subthreshold region show gate leakage similar to that of metal-semiconductor FETs. For the thicker n-AlGaAs layer, the subthreshold transfer characteristic shows additional conduction with sporadic current-spikes. We attribute the cause of sporadic current-spikes to deep donors or DX centers in the silicon-doped AlGaAs layer.