New trends in GaAs-based devices for generation of millimeter and submillimeter waves

Two examples of GaAs-based devices which can generate radiation with frequencies above 100 GHz are described. The first one is the InGaAs/InP pseudomorphic HEMT which consists of Al-free 2-DEG material structure. Optimization steps towards an improvement of its performance are described. From the analysis of the resulting device, an 0.1 /spl mu/m T-gate pHEMT with f/sub T//f/sub max/ of 160/300 GHz, is demonstrated. Obtained cutoff frequencies are comparable to the record values reported on InGaAs/InAlAs HEMTs, however Al-free devices show higher breakdown voltages, no kink effects and better reliability. Another novel device is an MSM detector on nonstoichiometric GaAs which is suitable as a radiation source up to THz frequency range using optical heterodyne mixing. Intrinsic and extrinsic bandwidths of a detector as well as conditions for output power increase are analyzed. A 3-dB bandwidth of 550 GHz, higher than previously reported, is achieved on an optimized device with interdigitated finger contacts. Further possibilities in performance improvement of both types of GaAs-based devices are finally discussed.