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Silicon Quantum Dots with Counted Antimony Donor Implants

Sandia journal manuscript; Not yet accepted for publication

Singh, Meenakshi S.; Pacheco, Jose L.; Perry, Daniel L.; Ten Eyck, Gregory A.; Wendt, J.R.; Pluym, Tammy P.; Dominguez, Jason J.; Manginell, Ronald P.; Luhman, Dwight R.; Bielejec, Edward S.; Lilly, Michael L.; Carroll, Malcolm

Deterministic control over the location and number of donors is crucial to donor spin quantum bits (qubits) in semiconductor based quantum computing. A focused ion beam is used to implant close to quantum dots. Ion detectors are integrated next to the quantum dots to sense the implants. The numbers of ions implanted can be counted to a precision of a single ion. Regular coulomb blockade is observed from the quantum dots. Charge offsets indicative of donor ionization, are observed in devices with counted implants.

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TYPE Journal Article YEAR 2015
OSTIOSTI

Mechanical Flip-Chip for Ultra-High Electron Mobility Devices

Scientific Reports

Bennaceur, Keyan; Schmidt, Benjamin A.; Gaucher, Samuel; Laroche, D.; Lilly, Michael L.; Reno, J.L.; West, Ken W.; Pfeiffer, Loren N.; Gervais, Guillaume

Electrostatic gates are of paramount importance for the physics of devices based on high-mobility two-dimensional electron gas (2DEG) since they allow depletion of electrons in selected areas. This field-effect gating enables the fabrication of a wide range of devices such as, for example, quantum point contacts (QPC), electron interferometers and quantum dots. To fabricate these gates, processing is usually performed on the 2DEG material, which is in many cases detrimental to its electron mobility. Here we propose an alternative process which does not require any processing of the 2DEG material other than for the ohmic contacts. This approach relies on processing a separate wafer that is then mechanically mounted on the 2DEG material in a flip-chip fashion. This technique proved successful to fabricate quantum point contacts on both GaAs/AlGaAs materials with both moderate and ultra-high electron mobility.

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TYPE Journal Article YEAR 2015
DOIOSTIScopus

Transport spectroscopy of low disorder silicon tunnel barriers with and without Sb implants

Nanotechnology

Carroll, Malcolm; Wendt, J.R.; Bishop, Nathaniel B.; Dominguez, Jason J.; Lilly, Michael L.; Shirkhorshidian, A.

We present transport measurements of silicon MOS split gate structures with and without Sb implants. We observe classical point contact (PC) behavior that is free of any pronounced unintentional resonances at liquid He temperatures. The implanted device has resonances superposed on the PC transport indicative of transport through the Sb donors. We fit the differential conductance to a rectangular tunnel barrier model with a linear barrier height dependence on source-drain voltage and non-linear dependence on gate bias. Effects such as Fowler-Nordheim (FN) tunneling and image charge barrier lowering (ICBL) are considered. Barrier heights and widths are estimated for the entire range of relevant biases. The barrier heights at the locations of some of the resonances for the implanted tunnel barrier are between 15-20 meV, which are consistent with transport through shallow partially hybridized Sb donors. The dependence of width and barrier height on gate voltage is found to be linear over a wide range of gate bias in the split gate geometry but deviates considerably when the barrier becomes large and is not described completely by standard 1D models such as FN or ICBL effects.

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TYPE Journal Article YEAR 2015
DOIOSTIScopus

Cryogenic Preamplification of a Single-Electron-Transistor using a Silicon-Germanium Heterojunction-Bipolar-Transistor

Applied Physics Letters

Curry, Matthew J.; England, Troy D.; Bishop, Nathaniel; Ten Eyck, Gregory A.; Wendt, J.R.; Pluym, Tammy P.; Lilly, Michael L.; Carr, Stephen M.; Carroll, Malcolm

We examine a silicon-germanium heterojunction bipolar transistor (HBT) for cryogenic pre-amplification of a single electron transistor (SET). The SET current modulates the base current of the HBT directly. The HBT-SET circuit is immersed in liquid helium, and its frequency response from low frequency to several MHz is measured. The current gain and the noise spectrum with the HBT result in a signal-to-noise-ratio (SNR) that is a factor of 10–100 larger than without the HBT at lower frequencies. Furthermore, the transition frequency defined by SNR = 1 has been extended by as much as a factor of 10 compared to without the HBT amplification. The power dissipated by the HBT cryogenic pre-amplifier is approximately 5 nW to 5 μW for the investigated range of operation. We found that the circuit is also operated in a single electron charge read-out configuration in the time-domain as a proof-of-principle demonstration of the amplification approach for single spin read-out.

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TYPE Journal Article YEAR 2015
DOIOSTI
Results 76–100 of 219
Results 76–100 of 219