HTS mixers based on the Josephson effect and on the hot-electron bolometric effect

We report on our experimental studies of high-T/sub c/ Josephson mixers and high-T/sub c/ hot-electron bolometric (HEB) effect mixers. Mixers based on high-T/sub c/ bicrystal Josephson junctions have been fabricated, and noise, conversion efficiency, and receiver bandwidth measurements have been performed in the frequency range between 90 and 550 GHz. The dependence of the mixer performance on the operation temperature has been studied. High-T/sub c/ HEB mixers have been fabricated on MgO and sapphire substrates. We successfully sized the dimensions of the effective device volume down and managed to fabricate 50-60 nm long devices. In such short structures phonon diffusion into the normal metal electrodes should significantly improve the mixer performance.