Study of IF Bandwidth of ${\hbox{MgB}}_{2}$ Phonon-Cooled Hot-Electron Bolometer Mixers

Abstract

A noise bandwidth (NBW) of 6-7 GHz was obtained for hot-electron bolometer (HEB) mixers made of 10 nm MgB films. A systematic investigation of the (IF) gain bandwidth as a function of the MgB film thickness (30, 15, and 10 nm) is also presented. The gain bandwidth (GBW) of 3.4 GHz was measured for a 10 nm film, corresponding to a mixer time constant of 47 ps. For 10 nm films a reduction of the GBW was observed with the reduction of the critical temperature . Experimental data were analyzed using the two-temperature model. From the theoretical analysis, the electron-phonon time -, the phonon escape time and the electron and phonon specific heats were extrapolated giving the first model for HEB mixers of MgB films.

MgB2 hot electron bolometer mixers for THz heterodyne instruments

“…8 However, the gain bandwidth was approximately 2GHz and the noise bandwidth of 4GHz. The promise of a much wider GBW (8-10GHz, based on the measured electron-phonon interaction time and the phonon escape time 9 ) has not been achieved. The utilized MgB 2 thin films, made by Molecular Beam Epitaxy, were 10-20nm thick with a superconducting transition temperature (T c ) 20-10K.…”

THz Hot-Electron Bolometer mixers

“…Even for a relatively high Tc NbN HEBs the mixer noise temperature starts to rise almost immediately for temperatures above 4K. However, for an MgB 2 HEB mixer a constant noise temperature was observed way up to 10 K [15]. This fact opens prospects for HEB mixer operation at temperatures higher than LHe.…”

Effect of the Critical and Operational Temperatures on the Sensitivity of HEB Mixers

“…A GBW of 2-3 GHz was reported both for thicker films with a higher T c (20nm, 20K) and for thin films with a much lower Tc (10nm, 9K) [18], [19]. A possibility of achieving a GBW of 8-10GHz with HEB mixers made from thin films with a high T c was also suggested in [20], which was recently confirmed in experimental work by Cunnane et al [22]. In that paper a GBW of 7 GHz (at 9K) and 8GHz (at 25K) was demonstrated for a device made from a 15nm thick MgB 2 film with a T c of 33 K. A feasibility of achievement of a low Tr was already demonstrated in the first publications on the MgB 2 HEB mixers, which allowed for measurements of the mixer noise bandwidth (NBW), as a more appropriate criterion for the HEB mixer performance assessment.…”

“…For devices with a higher T c, a higher Tr was observed (e.g. 1800K in [20]), but a NBW was more superior . For the device with a T c of 33K a T r of 3900K was measured [22].…”