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.