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

TL;DR

This paper demonstrates a single-gate controlled InGaAs quantum dot with integrated charge sensing, achieving high sensitivity and detailed charge state analysis, advancing quantum dot fabrication and measurement techniques.

Contribution

It introduces a novel double-quantum-well design with a single-gate accumulation-mode quantum dot and integrated charge sensor, enabling precise charge detection.

Findings

Charge sensitivity of 8.6% per electron

Single-electron detection with SNR of ~9:1

Measured electron tunneling lifetimes of 0.38 ms and 0.22 ms

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.