Low noise terahertz MgB2 hot-electron bolometer mixers with an 11GHz bandwidth

Terahertz (THz) hot-electron bolometer mixers reach a unique combination of low noise, wide noise bandwidth, and high operation temperature when 6nm thick superconducting MgB2 films are used. We obtained a noise bandwidth of 11GHz with a minimum receiver noise temperature of 930K with a 1.63THz Local Oscillator (LO) and a 5K operation temperature. At 15K and 20K, the noise temperature is 1100K and 1600K, respectively. From 0.69THz to 1.63THz the receiver noise increases by only 12%. Device current-voltage characteristics are identical when pumped with LOs from 0.69THz up to 2.56THz, and match well with IVs at elevated temperatures. Therefore, the effect of the THz waves on the mixer is totally thermal, due to absorption in the π conduction band of MgB2