Large bandwidth of NbN phonon-cooled hot-electron bolometer mixers on sapphire substrates.

摘要: The bandwidth of NbN phonon-cooled hot electron bolometer mixers has been systematically investigated with respect to the film thickness and quality variation. films, 2.5 10 mm thick, were fabricated on sapphire substrates using DC reactive magnetron sputtering. All devices consisted several parallel strips, each 1 1.1 wide 211 long, placed between Ti-Au contact pads. To measure gain we used two identical BWOs operating in 120-140 GHz frequency range, one functioning as a local oscillator other signal source. majority measurements made at an ambient temperature 4.5 K optimal LO bias. maximum 3 dB (about 4 GHz) was achieved for films which 2.5-3.5 nm had high critical temperature, current density. A theoretical analysis these based two-temperature model gives good description experimental results if assumes that is equal temperature.