Step-recessed gate GaAs FETs with an undoped surface layer

A step-recessed gate GaAs power FET with an undoped surface layer, which clads the n-GaAs channel, has been developed to simultaneously obtain a power-added efficiency (PAE) of more than 40% and a single-chip output power of more than 4 W in the class-A operation at the Ku-band. The undoped surface layer has been found to be effective for suppressing the frequency dispersion phenomena caused by a surface trapping effect and for raising the power level. The gate structure, with an undoped layer underneath the gate metal, has been found to be effective for improving the breakdown voltage, reducing the gate capacitance, and achieving high PAE. To the authors´ knowledge, these RF power performances with high linear gain represent the best data at 12 GHz.<>