Reduction of charge noise in shallow GaAs/AlGaAs heterostructures with insulated gates

Previous measurements utilizing Maxwell relations to measure change in entropy, S, demonstrated remarkable accuracy in measuring the spin-1/2 entropy of electrons in a weakly coupled quantum dot. However, these previous measurements relied upon prior knowledge of the charge transition lineshape. This had the benefit of making the quantitative determination of entropy independent of scale factors in the measurement itself but at the cost of limiting the applicability of the approach to simple systems. To measure the entropy of more exotic mesoscopic systems, a more flexible analysis technique may be employed; however, doing so requires a precise calibration of the measurement. Here, we give details on the necessary improvements made to the original experimental approach and highlight some of the common challenges (along with strategies to overcome them) that other groups may face when attempting this type of measurement.

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and

[ 18 , 19 ]. It is therefore crucial that the measurements

and

be carried out as close to each other in time as possible, protecting the measurement from noise in the low- f limit.…”

Section: Measurement Protocolmentioning

confidence: 99%

A Robust Protocol for Entropy Measurement in Mesoscopic Circuits

Child

Sheekey

Lüscher

et al. 2022

Entropy

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“…Quantum dots fabricated in GaAs/AlGaAs heterostructures experience intrinsic, albeit small, electrostatic fluctuations due to nearby charge motion in the dopant layer of the heterostructure, resulting in noise in the QD energy with a frequency spectrum typically between 1/f and 1/f 2 [16,17]. It is therefore crucial that the measurements N (T + ∆T ) and N (T ) be carried out as close to each other in time as possible, protecting the measurement from noise in the low-f limit.…”

Section: Measurement Protocolmentioning

confidence: 99%

A robust protocol for entropy measurement in mesoscopic circuits

Child,

Sheekey,

Lüscher

et al. 2021

Preprint

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Previous measurements utilizing Maxwell relations to measure change in entropy, S, demonstrated remarkable accuracy of measuring the spin-1/2 entropy of electrons in a weakly coupled quantum dot. However, these previous measurements relied upon prior knowledge of the charge transition lineshape. This had the benefit of making the determination of entropy independent of measurement scaling, but at the cost of limiting the applicability of the approach to relatively simple systems. To measure entropy of more exotic mesoscopic systems, a new analysis technique can be employed; however, doing so requires precise knowledge of the measurement scaling. Here, we give details on the necessary improvements made to the original experimental approach and highlight some of the common challenges (along with strategies to overcome them) that other groups may face when attempting this type of measurement.

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“…Moreover, surface charge increases unwanted charge‐noise in sensitive quantum electronic devices such as quantum wires, quantum dots, and spin‐based qubits. [ 11–14 ]…”

Section: Introductionmentioning

confidence: 99%

Ultra‐Shallow All‐Epitaxial Aluminum Gate GaAs/Al_xGa_1−xAs Transistors with High Electron Mobility

Alava

Wang

Chen

et al. 2021

Adv Funct Materials

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The electron mobility in shallow GaAs/AlxGa1−xAs heterostructures is strongly suppressed by charge wafer surface, which arises from native surface oxide layers formed when the wafer is removed from the crystal growth system. Here an in situ epitaxial aluminum gate, grown as part of the wafer, is used to eliminate surface charge scattering. Transmission electron microscope characterization shows that the in situ epitaxial aluminum is crystalline, and the wafer surface is free of native oxide. The influence of Al thickness and the use of different semiconductor wetting layers at the semiconductor‐aluminum interface are examined and correlated with electron mobility. The electron mobility is found to strongly depend on aluminum thickness. For 8 nm thick aluminum, the electron mobility is also influenced by the wetting layer, with aluminum grown on GaAs producing higher mobility compared to AlAs or Al0.33Ga0.67As wetting layers. The suppression of surface charge scattering in these all‐epitaxial devices allows for high mobilities across a wide density range despite the shallow conduction channel (35 nm below the gate). These measurements also provide a uniquely sensitive method of determining the electrical quality of the semiconductor–metal interface, relevant to the formation of hybrid semiconductor–superconductor devices.

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Reduction of charge noise in shallow GaAs/AlGaAs heterostructures with insulated gates

Cited by 6 publications

References 25 publications

A Robust Protocol for Entropy Measurement in Mesoscopic Circuits

A Robust Protocol for Entropy Measurement in Mesoscopic Circuits

A robust protocol for entropy measurement in mesoscopic circuits

Ultra‐Shallow All‐Epitaxial Aluminum Gate GaAs/Al_xGa_1−xAs Transistors with High Electron Mobility

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Reduction of charge noise in shallow GaAs/AlGaAs heterostructures with insulated gates

Cited by 6 publications

References 25 publications

A Robust Protocol for Entropy Measurement in Mesoscopic Circuits

A Robust Protocol for Entropy Measurement in Mesoscopic Circuits

A robust protocol for entropy measurement in mesoscopic circuits

Ultra‐Shallow All‐Epitaxial Aluminum Gate GaAs/AlxGa1−xAs Transistors with High Electron Mobility

Contact Info

Product

Resources

About

Ultra‐Shallow All‐Epitaxial Aluminum Gate GaAs/Al_xGa_1−xAs Transistors with High Electron Mobility