Single-shot measurement and tunnel-rate spectroscopy of a Si/SiGe few-electron quantum dot

Thalakulam, Madhu; Simmons, C. B.; Bael, B. J. Van; Rosemeyer, B. M.; Savage, D. E.; Lagally, M. G.; Friesen, Mark; Coppersmith, S. N.; Eriksson, M. A.

doi:10.1103/physrevb.84.045307

Cited by 22 publications

(24 citation statements)

References 34 publications

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“…Significant progress toward achieving coherent control of spins in single and double quantum dots in Si/SiGe have been suggested recently. [1][2][3][4][5] Long decoherence times in silicon have been achieved, 6 in large part, through enrichment of the Si with the zero nuclear spin isotope 28 Si. In SiGe/Si quantum dots, the wave function is in close proximity with a distribution of germanium nuclei in the SiGe barrier region.…”

Section: Introductionmentioning

confidence: 99%

Nuclear spin induced decoherence of a quantum dot in Si confined at a SiGe interface: Decoherence dependence on73Ge

2012

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We theoretically study the nuclear spin induced decoherence of a quantum dot in Si that is confined at a SiGe interface. We calculate decoherence time dependence on 73 Ge in the barrier layer to evaluate the importance of Ge as well as Si enrichment for long decoherence times. We use atomistic tight-binding modeling for an accurate account of the electron wave function which is particularly important for determining the contact hyperfine interactions with the Ge nuclear spins. We find decoherence times due to Ge spins at natural concentrations to be milliseconds. This suggests that SiGe/Si quantum dot devices employing enriched Si will require enriched Ge as well in order to benefit from long coherence times. We provide a comparison of T 2 times for various fractions of nonzero spin isotopes of Si and Ge.

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Section: Introductionmentioning

confidence: 99%

Nuclear spin induced decoherence of a quantum dot in Si confined at a SiGe interface: Decoherence dependence on73Ge

2012

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“…Transport spectroscopy, itself, is a relatively rapid way to characterize tunnel barriers relative to more time intensive and complex pulsing approaches used for these kinds of barriers. [27][28][29] The combination of this method with transport spectroscopy offers a relatively rapid way to build a compact model of a tunnel barrier for multiple gate electrodes and reasonably large bias ranges. This work should provide useful insight about the details of electrostatic barriers and how to characterize them.…”

Section: Discussionmentioning

confidence: 99%

Spectroscopy of Multielectrode Tunnel Barriers

et al. 2018

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Despite their ubiquity in nanoscale electronic devices, the physics of tunnel barriers has not been developed to the extent necessary for the engineering of devices in the few-electron regime. This problem is of urgent interest, as this is the precise regime into which current, extreme-scale electronics fall. Here, we propose theoretically and validate experimentally a compact model for multi-electrode tunnel barriers, suitable for design-rules-based engineering of tunnel junctions in quantum devices. We perform transport spectroscopy at T = 4 K, extracting effective barrier heights and widths for a wide range of biases, using an efficient Landauer-Büttiker tunneling model to perform the analysis. We find that the barrier height shows several regimes of voltage dependence, either linear or approximately exponential. The exponential dependence approximately correlates with the formation of an electron channel below an electrode. Effects on transport threshold, such as metal-insulator-transition and lateral confinement are non-negligible and included. We compare these results to semi-classical solutions of Poisson's equation and find them to agree qualitatively. Finally, we characterize the sensitivity of a tunnel barrier that is raised or lowered without an electrode being directly above the barrier region. arXiv:1705.01183v2 [cond-mat.mes-hall]

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“…To probe the excited states of the dot, pulsedgate spectroscopy was performed, with a square wave voltage applied to gate R enabling loading of excited states [39,40]. The gate lever arms used to convert the voltage on gate R to the electrostatic energy of the right dot are α R,RD = 78 µeV/mV for the 0-to-1 electron transition and α R,RD = 45 µeV/mV for the 1-to-2 electron transition and were extracted from the slope of the transition lines in Figures 3b,c.…”

Section: Resultsmentioning

confidence: 99%

Characterization of a gate-defined double quantum dot in a Si/SiGe nanomembrane

Knapp

Mohr

et al. 2016

Nanotechnology

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Abstract. We report the fabrication and characterization of a gate-defined double quantum dot formed in a Si/SiGe nanomembrane. In the past, all gatedefined quantum dots in Si/SiGe heterostructures were formed on top of straingraded virtual substrates. The strain grading process necessarily introduces misfit dislocations into a heterostructure, and these defects introduce lateral strain inhomogeneities, mosaic tilt, and threading dislocations. The use of a SiGe nanomembrane as the virtual substrate enables the strain relaxation to be entirely elastic, eliminating the need for misfit dislocations. However, in this approach the formation of the heterostructure is more complicated, involving two separate epitaxial growth procedures separated by a wet-transfer process that results in a buried non-epitaxial interface 625 nm from the quantum dot. We demonstrate that in spite of this buried interface in close proximity to the device, a double quantum dot can be formed that is controllable enough to enable tuning of the inter-dot tunnel coupling, the identification of spin states, and the measurement of a singlet-to-triplet transition as a function of an applied magnetic field.

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Single-shot measurement and tunnel-rate spectroscopy of a Si/SiGe few-electron quantum dot

Cited by 22 publications

References 34 publications

Nuclear spin induced decoherence of a quantum dot in Si confined at a SiGe interface: Decoherence dependence on73Ge

Nuclear spin induced decoherence of a quantum dot in Si confined at a SiGe interface: Decoherence dependence on73Ge

Spectroscopy of Multielectrode Tunnel Barriers

Characterization of a gate-defined double quantum dot in a Si/SiGe nanomembrane

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