Physics – Condensed Matter – Mesoscale and Nanoscale Physics
Scientific paper
2009-10-19
Appl. Phys. Lett. Vol. 96, 042101 (2010)
Physics
Condensed Matter
Mesoscale and Nanoscale Physics
3 pages, 3 figures
Scientific paper
10.1063/1.3280368
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.
Borselli Matthew G.
Bui Steven S.
Croke Edward T.
Gyure Mark F.
Hunter Andrew T.
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