Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Log inSign up
Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Blog
Job Board
Q3AS

© 2026 Aqora Quantum S.A.S.

TermsPrivacyLegal Notice

arXiv:1102.4544 · Applied Physics Letters

Si/SiGe quantum dot with superconducting single-electron transistor charge sensor

Mingyun Yuan, Feng Pan, Zhen Yang, T. J. Gilheart, Fei Chen, D. E. Savage, M. G. Lagally, M. A. Eriksson, A. J. Rimberg

Published Apr 4, 2011• 15 citations
arXivHTMLPDF

Abstract

We report a robust process for fabrication of surface-gated Si/SiGe quantum dots (QDs) with an integrated superconducting single-electron transistor (SSET) charge sensor. A combination of a deep mesa etch and AlOx backfill is used to reduce gate leakage. After the leakage current is suppressed, Coulomb oscillations of the QD and the current-voltage characteristics of the SSET are observed at a temperature of 0.3 K. Coupling of the SSET to the QD is confirmed by using the SSET to perform sensing of the QD charge state.

DOI
10.1063/1.3572033

Related papers

Charge sensing in a Si/SiGe quantum dot with a radio frequency superconducting single-electron transistor

Mingyun Yuan, Zhen Yang, D. E. Savage +3 more

We report the operation of a radio frequency superconducting single-electron transistor (rf-SSET) as a charge sensor for single and double Si/SiGe quantum dots (QDs). Real-time electron tunneling events are observed from the reflected signal of the rf-SSET with a charge sensitivity of 4×10−6 e/Hz, which demonstrates a fast charge detection time of a few tens of microseconds. Measurements of the reflected power are used to map out the stability diagram of the double quantum dot.

Applied Physics Letters•Oct 1, 2012•12 citations

Lateral electron tunneling through single self-assembled InAs quantum dots coupled to superconducting nanogap electrodes

Kenji Shibata, Christo Buizert, A. Oiwa +2 more

The authors have fabricated superconductor-quantum dot-superconductor (SC-QD-SC) junctions by using SC aluminum electrodes with narrow gaps laterally contacting a single self-assembled InAs QD. The fabricated junctions exhibited clear Coulomb staircases and Coulomb oscillations at 40mK. Furthermore, clear suppression in conductance was observed for the source-drain voltage, ∣VSD∣<2Δ∕e, where Δ is the SC energy gap of Al. The absence of Josephson current that flows through QDs is due to the strong Coulomb interaction and non-negligible thermal fluctuation in our measurement system.

arXiv:0711.1945•Applied Physics Letters•Sep 10, 2007•23 citations

Optimization of charge sensitivity of a single electron tunneling transistor with a superconducting grain

Ulrik Hanke, K. A. Chao, Y. M. Galperin

Assuming the absence of 1/f noise, we have calculated the charge sensitivity (CS) of a capacitive-coupled double-junction single electron tunneling transistor (SETT) with a superconducting grain, operating at low temperature and low bias voltage such that the tunneling current is dominated by the Andreev process. In this case the effect of co-tunneling is suppressed without using the complicated fabrication method. We have used a realistic sample to demonstrate the procedure of optimizing the CS of a SETT with respect to relevant physical parameters and structure parameters. With the presently available fabrication technology, our theoretical analysis can serve as a guide for increasing the CS of a SETT beyond 10−6 e/√Hz.

Journal of Applied Physics•Jul 15, 1996•0 citations

Circuit quantum electrodynamics architecture for gate-defined quantum dots in silicon

X. Mi, J. V. Cady, D. M. Zajac +3 more

We demonstrate a hybrid device architecture where the charge states in a double quantum dot (DQD) formed in a Si/SiGe heterostructure are read out using an on-chip superconducting microwave cavity. A quality factor Q = 5400 is achieved by selectively etching away regions of the quantum well and by reducing photon losses through low-pass filtering of the gate bias lines. Homodyne measurements of the cavity transmission reveal DQD charge stability diagrams and a charge-cavity coupling rate gc/2π= 23 MHz. These measurements indicate that electrons trapped in a Si DQD can be effectively coupled to microwave photons, potentially enabling coherent electron-photon interactions in silicon.

arXiv:1610.05571•Applied Physics Letters•Jan 23, 2017•94 citations

Spectroscopy of charge states of a superconducting single-electron transistor in an engineered electromagnetic environment

Eisuke Abe, Yuki Kimura, Y. Hashimoto +2 more

We study charge states of a superconducting single-electron transistor (SSET) fabricated on a heterostructure substrate that can be switched from insulating to conductive. We probe the charge states by microwave irradiation and subsequent observation of photon-assisted Josephson quasiparticle current, which allow us to obtain the energy dispersion relation in the quasicharge space. When the substrate is insulating, the charge states show an energy-dispersion curve with a gap, manifesting that coherent superposition of the two charge states is realized. When the substrate becomes conductive, its two-dimensional electrons capacitively couple to the SSET and modify the degree of dissipation to its electromagnetic environment. The dispersion relation then becomes linear, and its slope agrees with the value estimated from the charging energy including the capacitance of the two-dimensional electrons. This indicates that quantum coherence between the two charge states is lost due to the coupling with the environment.

Journal of Physics Conference Series•Mar 1, 2009•0 citations

Single-charge devices with ultrasmall Nb∕AlOx∕Nb trilayer Josephson junctions

R. Dolata, Hansjorg Scherer, Alexander B Zorin +1 more

Josephson junction transistors and 50-junction arrays with linear junction dimensions from 200nm down to 70nm were fabricated from standard Nb∕AlOx∕Nb trilayers. The fabrication process includes electron beam lithography, dry etching, anodization, and planarization by chemical-mechanical polishing. The samples were characterized at temperatures down to 25mK. In general, all junctions are of high quality and their I-U characteristics show low leakage currents and high superconducting energy gap values of Δ≈1.35meV. The characteristics of the transistors and arrays exhibit some features in the subgap area, associated with tunneling of Cooper pairs, quasiparticles, and their combinations due to the redistribution of the bias voltage between the junctions. Total island capacitances of the transistor samples ranged from 1.5fF to 4fF, depending on the junction sizes. Devices made of junctions with linear dimensions below 100nm×100nm demonstrate a remarkable single-electron behavior in both superconducting and normal state. We also investigated the area dependence of the junction capacitances for transistor and array samples.

arXiv:cond-mat/0410288•Journal of Applied Physics•Feb 4, 2005•37 citations
We report a robust process for fabrication of surface-gated Si/SiGe quantum dots (QDs) with an integrated superconducting single-electron transistor (SSET) charge sensor. A combination of a deep mesa etch and AlOx backfill is used to reduce gate leakage. After the leakage current is suppressed, Coulomb oscillations of the QD and the current-voltage characteristics of the SSET are observed at a temperature of 0.3 K. Coupling of the SSET to the QD is confirmed by using the SSET to perform sensing of the QD charge state.
The authors have fabricated superconductor-quantum dot-superconductor (SC-QD-SC) junctions by using SC aluminum electrodes with narrow gaps laterally contacting a single self-assembled InAs QD. The fabricated junctions exhibited clear Coulomb staircases and Coulomb oscillations at 40mK. Furthermore, clear suppression in conductance was observed for the source-drain voltage, ∣VSD∣<2Δ∕e, where Δ is the SC energy gap of Al. The absence of Josephson current that flows through QDs is due to the strong Coulomb interaction and non-negligible thermal fluctuation in our measurement system.
Assuming the absence of 1/f noise, we have calculated the charge sensitivity (CS) of a capacitive-coupled double-junction single electron tunneling transistor (SETT) with a superconducting grain, operating at low temperature and low bias voltage such that the tunneling current is dominated by the Andreev process. In this case the effect of co-tunneling is suppressed without using the complicated fabrication method. We have used a realistic sample to demonstrate the procedure of optimizing the CS of a SETT with respect to relevant physical parameters and structure parameters. With the presently available fabrication technology, our theoretical analysis can serve as a guide for increasing the CS of a SETT beyond 10−6 e/√Hz.
We demonstrate a hybrid device architecture where the charge states in a double quantum dot (DQD) formed in a Si/SiGe heterostructure are read out using an on-chip superconducting microwave cavity. A quality factor Q = 5400 is achieved by selectively etching away regions of the quantum well and by reducing photon losses through low-pass filtering of the gate bias lines. Homodyne measurements of the cavity transmission reveal DQD charge stability diagrams and a charge-cavity coupling rate gc/2π= 23 MHz. These measurements indicate that electrons trapped in a Si DQD can be effectively coupled to microwave photons, potentially enabling coherent electron-photon interactions in silicon.
We study charge states of a superconducting single-electron transistor (SSET) fabricated on a heterostructure substrate that can be switched from insulating to conductive. We probe the charge states by microwave irradiation and subsequent observation of photon-assisted Josephson quasiparticle current, which allow us to obtain the energy dispersion relation in the quasicharge space. When the substrate is insulating, the charge states show an energy-dispersion curve with a gap, manifesting that coherent superposition of the two charge states is realized. When the substrate becomes conductive, its two-dimensional electrons capacitively couple to the SSET and modify the degree of dissipation to its electromagnetic environment. The dispersion relation then becomes linear, and its slope agrees with the value estimated from the charging energy including the capacitance of the two-dimensional electrons. This indicates that quantum coherence between the two charge states is lost due to the coupling with the environment.
Josephson junction transistors and 50-junction arrays with linear junction dimensions from 200nm down to 70nm were fabricated from standard Nb∕AlOx∕Nb trilayers. The fabrication process includes electron beam lithography, dry etching, anodization, and planarization by chemical-mechanical polishing. The samples were characterized at temperatures down to 25mK. In general, all junctions are of high quality and their I-U characteristics show low leakage currents and high superconducting energy gap values of Δ≈1.35meV. The characteristics of the transistors and arrays exhibit some features in the subgap area, associated with tunneling of Cooper pairs, quasiparticles, and their combinations due to the redistribution of the bias voltage between the junctions. Total island capacitances of the transistor samples ranged from 1.5fF to 4fF, depending on the junction sizes. Devices made of junctions with linear dimensions below 100nm×100nm demonstrate a remarkable single-electron behavior in both superconducting and normal state. We also investigated the area dependence of the junction capacitances for transistor and array samples.