PT Journal
AU Siddiqi, I
   Prober, DE
TI Nb–Au bilayer hot-electron bolometers for low-noise THz heterodyne detection
SO Applied Physics Letters
JI Appl. Phys. Lett.
PY 2004
BP 1404
VL 84
IS 8
DI 10.1063/1.1646726
DE HEB; mixers; dynamic range; saturation; LO power; local oscillator power; Nb
AB The sensitivity of present Nb diffusion-cooled hot-electron bolometer (HEB) mixers is not quantum limited, and can be improved by reducing the superconducting transition temperature TC. Lowering TC reduces thermal fluctuations, resulting in a decrease of the mixer noise temperature TM. However, lower TC mixers have reduced dynamic range and saturate more easily due to background noise. We present 30 GHz microwave measurements on a bilayer HEB system, Nb–Au, in which TC can be tuned with Au layer thickness to obtain the maximum sensitivity for a given noise background. These measurements are intended as a guide for the optimization of THz mixers. Using a Nb–Au mixer with TC = 1.6 K, we obtain TM = 50 K with 2 nW of local oscillator (LO) power. Good mixer performance is observed over a wide range of LO power and bias voltage and such a device should not exhibit saturation in a THz receiver.
ER