Noise and conversion efficiency of aluminum superconducting hot-electron bolometer mixer

We report on microwave measurements of superconducting aluminum hot-electro n bolometers (Al HEBs), Diffusion-cooled Al HEB mixers are good candidates for space-borne applications in the Terahertz frequency range since they ar e predicted to have small local oscillator (LO) power requirements, interme diate frequency (IF) bandwidths greater than or similar to 10 GHz, and a no ise temperature lower than that of Nb and NbN HEB mixers. Mixer measurement s were made at an LO frequency similar to 30 GHz, with an IF in the range 0 .1 to 7.3 GHz, For T < 0.8 K, a magnetic field H=0.1-0.3T was applied to su ppress the superconductivity in the contact pads, and partly in the bridge. For a 0.6 mum long device, we measure an IF bandwidth of 4 GHz, a conversi on efficiency eta = -8dB, and a mixer noise temperature T-M greater than or similar to 4K, DSB (T-mixer=T-output noise/2 eta). These results are shown to be in quantitative agreement with simple theoretical predictions.