Gain bandwidth of NbN hot-electron bolometer terahertz mixers on 1.5 μm Si_3N_4/SiO_2 membranes

摘要

The gain bandwidth of NbN hot-electron bolometer terahertz mixers on electrically thin Si_3N_4/SiO_2 membranes was experimentally investigated and compared with that of HEB mixers on bulk substrates. A gain bandwidth of 3.5 GHz is achieved on bulk silicon, whereas the gain bandwidth is reduced down to 0.6-0.9 GHz for mixers on 1.5μm Si_3N_4/SiO_2 membranes. We show that application of a MgO buffer layer on the membrane extends the gain bandwidth to 3 GHz. The experimental data were analyzed using the film-substrate acoustic mismatch approach.