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arXiv · 0910.3631

Single-Gate Accumulation-Mode InGaAs Quantum Dot with a Vertically Integrated Charge Sensor

E. T. Croke·M. G. Borselli·M. F. Gyure·S. S. Bui·I. I. Milosavljevic·R. S. Ross·A. E. Schmitz·A. T. Hunter
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Abstract

We report on the fabrication and characterization of a few-electron quantum dot controlled by a single gate electrode. Our device has a double-quantum-well design, in which the doping controls the occupancy of the lower well while the upper well remains empty under the free surface. A small air-bridged gate contacts the surface, and is positively biased to draw laterally confined electrons into the upper well. Electrons tunneling between this accumulation-mode dot and the lower well are detected using a quantum point contact (QPC), located slightly offset from the dot gate. The charge state of the dot is measured by monitoring the differential transconductance of the QPC near pinch-off. Addition spectra starting with N=0 were observed as a function of gate voltage. DC sensitivity to single electrons was determined to be as high as 8.6%, resulting in a signal-to-noise ratio of ~9:1 with an equivalent noise bandwidth of 12.1 kHz. Analysis of random telegraph signals associated with the zero to one electron transition allowed a measurement of the lifetimes for the filled and empty states of the one-electron dot: 0.38 ms and 0.22 ms, respectively, for a device with a 10 nm AlInAs tunnel barrier between the two wells.

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E. T. Croke, M. G. Borselli, M. F. Gyure, S. S. Bui, I. I. Milosavljevic, R. S. Ross, A. E. Schmitz, A. T. Hunter. 2009-10-19. Single-Gate Accumulation-Mode InGaAs Quantum Dot with a Vertically Integrated Charge Sensor. https://doi.org/10.1063/1.3280368

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