Monolithic fabrication of a planar Gunn diode and a pHEMT side-by-side

This work presents the implementation of planar Gunn diodes and pseudomorphic high electron mobility transistors (pHEMTs) on the same wafer for the first time. The AlGaAs/InGaAs/GaAs heterostructures were designed for the realisation of pHEMTs on a Gallium Arsenide - based wafer. T-gate technology has been used for the maximisation of the transistor performance. Devices with a 70 nm long gate foot showed excellent DC and small-signal characteristics, with 780 mS/mm peak transconductance and 200 GHz fmax. Planar Gunn diodes were fabricated in parallel with the pHEMTs, sharing most of the fabrication steps. The diodes produce oscillations with 87.6 GHz maximum frequency and -40 dBm maximum output power.