High voltage operation in class B GaAs X-band power MESFETs

Abstract

Surface trapping effects are shown to affect adversely the RF power performance of high-voltage GaAs MESFETs and a model is presented to explain them. It is shown that the adverse effects of surface trapping can be minimized by: (1) including an undoped layer near the surface, (2) reducing the distance between the gate and n/sup +/ ledge, and (3) making the gate recess narrower than the gate. Devices fabricated with such a structure showed excellent RF power performance at 10 GHz: P/sub 0/=678 mW/mm, G /sub A/=6.8 dB, and eta /sub PA/=51.1% at a drain-bias voltage of 12 V. The design of devices to minimize surface-trapping effects is also expected to lead to self-passivating devices that will be inherently more reliable and show less 1/f noise. The high-voltage, high-efficiency devices described here will be applicable in airborne phased array radar systems where power supply requirements and heat dissipation problems limit system performance.<>