UVA-NRAO ALMA Development Proposal for Superconducting Circuits

PI:   Professor Arthur Lichtenberger
Amount: $3.57M
Duration: 5 years (start 09-2016)

The UVML has a long-standing internationally recognized program of excellence in THz materials, devices, circuits, and metrology. This effort began in the early 1970s with the pioneering development, in a historic collaboration with the NRAO, of semiconductor Schottky barrier diodes and later superconductor detectors for radio astronomy. The UVML has since closely collaborated with astronomical receiver groups and the NRAO for more than 30 years to develop state of the art superconducting receivers for use on radio telescopes throughout the world. Over the past decade, the UVML has collaborated with different astronomical group for the development of state of the art superconductive mixers for the international, >$1B Atacama Large Millimeter/submillimeter Array (ALMA) – the largest land based astronomy project in the world. The UVML has demonstrated SIS mixers that exceed the design specifications of ALMA’s bands 3 (84-116 GHz), 6 (211-275 GHz), 7 (275-370 GHz) and 8 (385-500 GHz), and is the SIS foundry for all Band3 and Band6 SIS mixer chips. The UVML was the first group to develop the SIS “SOI” mixer architecture with ultra-thin Si chips and Au beam leads and the first group to develop inductively coupled plasma (ICP) grown AlN tunnel barriers that have led to the highest quality Nb/Al-AlN/Nb and Nb/Al-AlN/NbTiN (NbTiN with a higher energy gap) SIS junctions. Our SOI architecture and AlN barriers are ripe for the NRAO’s exploitation for more sensitive, wideband and sideband receivers, better performing higher frequency second-generation receivers and array receivers.

The signature element of ALMA is a young international astronomical facility of unprecedented capabilities that is already producing new and important scientific results. ALMA’s continued long-term success is of critical importance to the NRAO, the North America (NA) millimeter and the international radio astronomy community. Realizing the next generation of ALMA SIS mixers that operate near their quantum limit will require new mixer designs, materials and advanced SIS circuit fabrication approaches. The primary goal of the proposed research and development is therefore to further the infrastructure of radio astronomy by working synergistically with the NRAO over the next five years to support and advance ALMA’s millimeter and submillimeter detector program. This work will include: (a) maintaining our Nb/Al-oxide/Nb SIS materials and fabrication capability, (b) maintaining our Band3 and Band 6 Nb/Al-oxide/Nb SIS mixer capability, (c) development of next generation Band 6, Band10 and potentially other ALMA prototype mixer wafers (this entails considerable body of work, detailed later), (d) continued development of additional superconducting circuit components (e.g., hybrids and couplers), (e) investigate wafer failure mechanisms and improve yield, (f) development of rapid SIS chip screening (cryo probe station, probes), and (g) development of sets of design rules (to be open to the community) for these different processes. This will enable our group to continue to be well positioned for ongoing as well as new and unforeseen collaborations that benefit the astronomical community. The technology we propose to develop is crucial to the astronomy community.


Left: backside of an array of UVA-NRAO prototype Band8 SOI mixer chips before release from the carrier wafer. Right: single Band8 SOI mixer chip comprising 3um thick Si and 2um thick Au beamleads.


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