Microwave mixers employing multiple-barrier semiconductor heterostructure devices

Experimental data on mixer performance of unipolar semiconductor heterostructure diodes containing bulk alloy-ramp barriers are presented. Prototype Al_xGa_1-xAs/GaAs heterostructures containing one, two, and four barriers are fabricated by MBE and tested in a single-ended mixer circuit at 10 GHz. The devices with two and four barriers, which exhibit improved performance over the single-barrier device, achieve conversion losses between 4 and 6 dB and noise temperature ratios between 1.5 and 2 at 300 K. Several significant advantages over contending Schottky diodes are also discussed. The results indicate that multiple-barrier devices are good candidates for use in microwave and millimeter-wave mixer circuits