Nb/Al-AlO_x/Nb junctions for a 380 GHz SIS receiver

Abstract

To optimize this process, it has been useful to carry out several studies. We found that it was necessary to heat sink the quartz substrate during all trilayer fabrication steps. Anodization spectroscopy and RIE etching have been used to verity the quality of the tunnel barrier which is directly correlated with the I-V characteristics. An oxygen plasma is used to reduce the resist diameter and thus to expose the junction perimeter to the Si0 layer, so as to obtain small junction areas with small leakage currents. The first results obtained with these junctions integrated in a 380 GHz receiver are promising: the DSB receiver noise temperature is 310 K a t 374 GHz with a mixer noise temperature of about 155 K.

New elements for analysis of series arrays of superconducting junctions for submillimeter heterodyne detection

“…Some series arrays of two, three and four circular SIS junctions in series have been manufactured [12] for an SIS mixer designed to operate at 374 GHz on a balloon-borne receiver of the french space agency (CNES) 1161. The diameters of the junctions have been chosen to provide about the same total normal resistances RN in the range 110-150 ohms for each kind of array.…”

“…Very good performance has been obtained with such devices [5-71. However, conventional photolithography (for example see [12]) provides junctions with areas as small as one square-micron whose performances have been demonstrated up to 500 -550 GHz, either used as single or twin junctions [I-41 or in series arrays [6,8].…”

Antennas for Short Distance Communications in Cryogenic Environment

“…In this study, we have chosen to use antennas placed in near-field configuration to transmit data in the 8-12 GHz band. This frequency range has been chosen as a typical intermediate frequency range used for Superconductor-Insulated-Superconductor (SIS) mixers [3] cooled at 4 K for radioastronomy applications. The configuration is such that the emitting antenna plane is placed parallel to one of the cryogenic system thermal shield, while the receiving antenna is placed across from the emitting antenna and parallel to another thermal shield of a different temperature.…”