InAsOI chip

12 Mar Work progresses at CNR-NANO as Spectrum approaches conclusion

Posted at 16:51h in News by

With only a few weeks to go before the conclusion of the Spectrum project, the work of our partner CNR-NANO is focusing on pushing the frequency limits of superconducting Josephson Field Effect Transistors (JoFETs) made on the InAs on Insulator (InAsOI) platform within the operational range of superconducting transmon qubits.

In this photograph, it is possible to see an InAsOI chip featuring coplanar waveguides that are designed to route superconducting radiation directly to the fabricated JoFETs.

InAsOI chip

The manufacturing process, developed at the NEST laboratory (National Enterprise for NanoScience and NanoTechnology – Pisa, Italy) with CNR-NANO, CNR and Scuola Normale Superiore includes the following cutting-edge steps:

  • Ultra-high vacuum (1E-10 Torr) e-beam deposition of nanometric superconductors.
  • Thermal deposition of metallic thin films.
  • Over ten UV (385 nm) and EB (30 kV) lithography steps.
  • Wet chemical patterning of superconductors and III-V compounds.
  • Lift-off patterning of metallic thin films.
  • Atomic Layer Deposition of nanometric-thick high dielectric permittivity insulators.

This second image showcases our advanced measurement setup, implemented on the mixing chamber plate of a dilution refrigerator operating at a base temperature of 50 mK. This setup allows for:

  • Simultaneous DC and RF (up to 10 GHz) characterization of the device under test with cryogenic bias Ts.
  • Demultiplexed inputs and multiplexed outputs for efficient device testing.
  • Highly filtered and electron thermally coupled DC characterization.
  • Filtered and attenuated RF input lines to ensure signal thermalization and device integrity.
  • Superconducting RF output line with broad-band (100 MHz – 10 GHz) cryogenic amplification (30 dB) to boost the SNR.
  • Highly-trasmittive ad-hoc FR4 sample holders with Cu Faraday cages to suppress unwanted resonance modes until 10 GHz.

advanced measurement setup

This work is fully supported by Spectrum in the EIC – Transition Open programme framework under the supervision of Francesco Giazotto. Spectrum partners are intensifying their work before the end of the project, which is due by the end of April 2025.

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