Domaine Universitaire, 38406 St. M a r t i n dHeres, FranceAbstracfiAn ultra low noise SIS receiver has been prepared for radio astronomy. The minimum doub\e sideband receiver noise temperature is about 30 K which corresponds to 2 A& or an equivalent number of 4 photons of noise. The minimum measured double sideband mixer noise temperature is about 10 K which corresponds to 0.6 lolk or approximately to 1 photon of noise. The fixed tuned SIS mixer operates in the 290-370 GHz fkequency range. The submicron niobium junctions were fabricated using photoresist lines for junction definition. The receiver has been used at the 30 m IRAM radio telescope in Spain in winter 1994. Telescope system noise temperature of 500 K single sideband has been achieved when the sky opacity was about 0.17.

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W e describe our labricat on process 01 Nb-AI oxide No tunne junctions w.th integratea filter strbcture. Tne process includes t h e lin-on s1enc.l techniqLe and liquid anodization. The quality 01 the .dnctions witn areas aown to aboLt lpm' s discussed and the triiayers are analysed by anooization spectroscopy. Tne occurrence of proximity effect structures lor tri.ayers witn thicn (160 A) AI films ana lor lrilayers with poor anodization profiles is demonstrated Finally t h e mxer pedormance 01 a two-junction array IS o.itlinea .n the range arodnd 100 GHz.