On-State and Off-State Breakdown Voltages in GaAs PHEMTs With Various Field-Plate and Gate-Recess Extension Structures

GaAs pseudomorphic high-electron mobility transistors (PHEMTs) with various field-plate (FP) and gate-recess (GR) extensions were fabricated. Their on-state resistance ( R on ), breakdown voltage, flicker noise, and microwave characteristics were investigated. The FP length and GR width extensions can be controlled to improve significantly the breakdown voltage of PHEMTs. The design-of-experiment approach was employed with 16 transistors. The FP length extension was found to improve efficiently the off-state breakdown voltage ( BV off ) because of its suppression of the thermionic-field emission of gate electrons. However, an FP-induced depletion region cannot easily suppress channel impact ionization, which dominates the on-state breakdown voltage ( BV on ). Additionally, the FP length extension reduces the flicker noise of a device that is caused by surface states. The GR width extension has an opposite effect, because the exposed area of the uncap Schottky layer exposure increases with the GR width.