Dispersive Sensing of Holes in Silicon Fin Field-Effect Transistors*

Silicon is a promising host material for quantum dot (QD) spin qubits, offering long coherence and short gate times. Moreover, a scalable array of densely packed qubits can be envisaged by leveraging well-established industry standard fin-field-effect transistor (FinFET) technology. Recently, a hole spin qubit in FinFETs operating at 4.2K was demonstrated, showcasing fast, all-electrical qubit control [Camenzind et al. arXiv:2103.07369]. The small device footprint and high operation temperature are crucial for future scaling. Here, we report on gate-based reflectometry of hole-charge transitions in QDs formed in FinFET devices. For this purpose, a tank circuit on a dot-defining gate is probed resonantly. Tunnelling of holes in the vicinity of the gate alters the gate admittance that causes a dispersive shift of the reflected signal. Varactor diodes are integrated to tune impedance matching [Ares et al. PRA 5, 034011 (2016)]. We benchmark the resonator performance of commercial inductors as well as superconducting thin-film NbTiN inductors. Our results pave the way towards fast, single-shot readout of FinFET hole spin qubits at few-kelvin temperatures.