Superconducting Silicon and Germanium devices upscale – SUNISIDEUP

The aim of SUNISIDEUP is to realize, in an scalable CMOS technology, a silicon or germanium superconducting qubit, electrically controlled by a gate and coupled to a superconducting microwave resonator. This new quantum element, now called GATEMON by analogy with the transmon, will find applications in quantum information. This superconducting qubit will consist of a transistor with superconducting source and drain contacts through which a non-dissipative super-current (Josephson effect) can flow and be modulated by an electrostatic gate. For silicon devices, the superconducting contacts will be made from superconducting silicides or heavily boron doped silicon which is known to be superconducting at a very high dose. This technique requires the use of laser annealing. The germanium devices will benefit from a more flexible and less advanced technology but for which the Josepshon effect has already been demonstrated. Superconducting resonators will also be made from the same materials and an accurate and systematic study of their performance (through their quality factor) will be conducted.
In addition to the realization of new superconducting quantum elements, the real originality of the SUNISIDEUP project is to propose a technology that is fully compatible with CMOS technology and therefore potentially scalable. Thus, the success of SUNISIDEUP will quickly allow to realize complex quantum architectures inspired by the propositions already established by the superconducting qubits and the Quantum ElectroDynamics circuit QED community.
SUNISIDEUP will focus on two key objectives: i) the development of a new hybrid (quantum) technology combining superconductivity and CMOS technology with the realization of superconducting MOSFETs and new electrically controllable superconducting qubits; ii) the study of new electronic states in confined nanostructures where spin-orbit coupling and Coulomb interactions compete with superconducting correlations.
The project is organized into four workpackages: management, material synthesis, study of superconductor / semiconductor contacts and integration and lastly, low temperature quantum studies and manipulation. Our project is based on a highly targeted consortium that includes LETI and INAC / PHELIQS at CEA-Grenoble and C2N at Paris-Saclay. LETI will provide expertise in all aspects of MOSFET fabrication on SOI silicon-on-insulator wafers. The C2N partner, which has successfully demonstrated the superconductivity of boron-doped silicon, will bring its deep know-how on doping and laser annealing, which is a crucial technique for producing superconducting contacts with low ohmic resistance. The PHELIQS laboratory has a renowned knowledge, both experimental and theoretical, about the low temperature electronic transport properties of hybrid Josephson junctions and CMOS silicon quantum dots.
The fabrication of a large number of quantum devices with different size and shape in a well-controlled and reproducible technology is a strong potential of SUNISIDEUP. It gives the possibility tackle the problem of quantum variability which is known to be an important aspect for building complex architecture comprising a large number of quantum elements.