Low-temperature tunable radio-frequency resonator for sensitive dispersive readout of nanoelectronic devices

TL;DR

This paper introduces a sensitive, tunable RF resonator operable at dilution refrigerator temperatures, capable of detecting nanoelectronic device changes with high charge sensitivity, and demonstrates its effectiveness with silicon nanowire quantum dots.

Contribution

The work presents a novel low-temperature tunable RF resonator with GaAs varicap diodes, achieving significant frequency tuning and improved charge sensitivity for nanoelectronic device readout.

Findings

Resonant frequency tuning range of 8.4 to 29 MHz across temperature

Charge sensitivity improved from 43 to 31 μe/√Hz with re-tuning

High sensitivity achieved with impedance matching and low parasitic capacitance

Abstract

We present a sensitive, tunable radio-frequency resonator designed to detect reactive changes in nanoelectronic devices down to dilution refrigerator temperatures. The resonator incorporates GaAs varicap diodes to allow electrical tuning of the resonant frequency and the coupling to the input line. We find a resonant frequency tuning range of 8.4 MHz at 55 mK that increases to 29 MHz at 1.5 K. To assess the impact on performance of different tuning conditions, we connect a quantum dot in a silicon nanowire field-effect transistor to the resonator, and measure changes in the device capacitance caused by cyclic electron tunneling. At 250 mK, we obtain an equivalent charge sensitivity of $43~\mu e / \sqrt{\text{Hz}}$ when the resonator and the line are impedance-matched and show that this sensitivity can be further improved to $31~\mu e / \sqrt{\text{Hz}}$ by re-tuning the resonator. We understand this improvement by using an equivalent circuit model and demonstrate that for maximum sensitivity to capacitance changes, in addition to impedance matching, a high-quality resonator with low parasitic capacitance is desired.