Optimization of sample-chip design for stub-matched radio-frequency reflectometry measurements

TL;DR

This paper investigates and optimizes a tunable rf matching circuit for reflectometry in semiconductor nanostructures, demonstrating a threefold enhancement in measurement sensitivity through improved chip design.

Contribution

It introduces a method to optimize sample-specific chip design for rf reflectometry using a tunable varactor diode, achieving significant sensitivity improvements.

Findings

Reflection coefficient change can be increased by a factor of 3.

Optimized electrode geometry enhances measurement sensitivity.

Comparison of different chip designs shows significant performance differences.

Abstract

A radio-frequency (rf) matching circuit with an in situ tunable varactor diode used for rf reflectometry measurements in semiconductor nanostructures is investigated and used to optimize the sample-specific chip design. The samples are integrated in a 2-4 GHz stub-matching circuit consisting of a waveguide stub shunted to the terminated coplanar waveguide. Several quantum point contacts fabricated on a GaAs/AlGaAs heterostructure with different chip designs are compared. We show that the change of the reflection coefficient for a fixed change in the quantum point contact conductance can be enhanced by a factor of 3 compared to conventional designs by a suitable electrode geometry.