Barrier Height Engineering at V₃Si-Si Interfaces for Quantum Device Applications

The superconducting A15 phase of vanadium silicide (V₃Si) is a promising candidate for realizing novel Josephson junction-based quantum computing devices. V₃Si-Si based Josephson junctions can be used to fabricate voltage-controlled transmon qubits, also known as gatemons. Apart from higher temperatures of operation due to the higher T_c (~ 17 K) of V₃Si, these superconductor-insulator-superconductor type gatemons are also expected to have longer coherent times. Because V₃Si is almost perfectly lattice-matched to Si, fabrication of these qubits is compatible with existing CMOS technology.

In order to realize V₃Si-based gatemons, it is crucial to understand how the V₃S-Si Schottky barrier height is tuned by the carrier density in silicon. In this talk we report a method for reproducibly synthesizing superconducting vanadium silicide on Si substrates at various levels of doping and a systemic temperature-dependent transport study to determine the V₃S-Si Schottky barrier height. We observe that, as compared to undoped Si, doping increases the barrier transparency and reduces barrier height by an order of magnitude. It is observed that n-type doping in Si lowers the barrier height more than p-type doping.

These results evidence that V₃Si is a suitable platform for realizing voltage-based Josephson field effect transistors (JoFETs) and can have a significant broader impact in the field of semiconductor-based quantum computing research.