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Integrated impedance bridge for absolute capacitance measurements at cryogenic temperatures and finite magnetic fields

Journal Article (2019)
Author(s)

G. J. Verbiest (JARA-FIT and 2nd Institute of Physics)

H. Janssen (JARA-FIT and 2nd Institute of Physics)

D. Xu (Kavli institute of nanoscience Delft, TU Delft - QuTech Advanced Research Centre, TU Delft - QRD/Kouwenhoven Lab)

X. Ge (JARA-FIT and 2nd Institute of Physics)

M. Goldsche (Forschungszentrum Jülich, JARA-FIT and 2nd Institute of Physics)

J. Sonntag (Forschungszentrum Jülich, JARA-FIT and 2nd Institute of Physics)

T. Khodkov (JARA-FIT and 2nd Institute of Physics, Forschungszentrum Jülich)

L. Banszerus (Forschungszentrum Jülich, JARA-FIT and 2nd Institute of Physics)

N. Von Den Driesch (Forschungszentrum Jülich)

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Research Group
QRD/Kouwenhoven Lab
DOI related publication
https://doi.org/10.1063/1.5089207
More Info
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Publication Year
2019
Language
English
Research Group
QRD/Kouwenhoven Lab
Issue number
8
Volume number
90
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Abstract

We developed an impedance bridge that operates at cryogenic temperatures (down to 60 mK) and in perpendicular magnetic fields up to at least 12 T. This is achieved by mounting a GaAs HEMT amplifier perpendicular to a printed circuit board containing the device under test and thereby parallel to the magnetic field. The measured amplitude and phase of the output signal allows for the separation of the total impedance into an absolute capacitance and a resistance. Through a detailed noise characterization, we find that the best resolution is obtained when operating the HEMT amplifier at the highest gain. We obtained a resolution in the absolute capacitance of 6.4 aF/Hz at 77 K on a comb-drive actuator while maintaining a small excitation amplitude of 15 kBT/e. We show the magnetic field functionality of our impedance bridge by measuring the quantum Hall plateaus of a top-gated hBN/graphene/hBN heterostructure at 60 mK with a probe signal of 12.8 kBT/e.