High-Tc micro and nano-constrictions modeling: hot spot approach for DC characteristics and HEB THz mixer performance
Résumé
High-TC hot electron bolometers (HEB) are promising THz mixers due to their expected wide bandwidth, large mixing gain, and low intrinsic noise. We have simulated the characteristics of YBaCuO HEBs with a hot spot model usually dedicated to low-TC phonon cooled devices. With respect to e.g., NbN, the high-TC specificities are mainly arising from the large values of YBaCuO phonon thermal conductivity, and the film to MgO substrate phonon escape time. The consequent effects on the electron temperature profiles along the YBaCuO constriction and the current voltage DC characteristics are considered. The conversion gain G and noise temperature TN were computed for two constriction dimensions. For a 100 nm long × 100 nm wide × 10 nm thick constriction at 9 microwatt local oscillator (LO) power, the expected double sideband (DSB) TN = 1520 K (G = −13.7 dB). For a larger (but more realistic according to YBaCuO aging effects) 400 nm long × 400 nm wide × 35 nm thick constriction, minimum TN = 1210 K DSB at 35 microwatt LO power (G = −13.1 dB).