Abstract
The electronic structure of self-assembled semiconductor quantum dots consists of discrete atom-like states that can be populated with a well-defined number of electrons. This property can be used to fabricate a d.c. current standard that enables the unit of ampere to be independently defined. Here we report an optically pumped current source based on self-assembled InAs/GaAs quantum dots. The accuracy obtained so far is 10−1 and is limited by the uncertainty in the number of dots. At 10 K the device generates a current difference of 2.39 nA at a frequency of 1 kHz. The accuracy could be improved by site-selective growth techniques where the number of dots is fixed by pre-patterning. The results are promising for applications in electrical metrology, where a current standard is needed to close the so-called quantum metrological triangle.
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Acknowledgements
This work was supported by the Swiss National Foundation under the NCCR project Quantum Photonics. The authors would like to thank Tobias Gresch for providing the QCL used for the pump–probe measurement.
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L.N. carried out the measurements, did the data interpretation and wrote the manuscript. V.L. grew the samples by molecular beam epitaxy, processed the devices, followed the study and wrote the manuscript. F.C. contributed to the data interpretation, modelling and wrote the manuscript. A.B., P.F. and H.S. helped with the experiment. F.G. and E.M. provided the TEM pictures. The idea came from J.F. and all work was done under his supervision.
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Nevou, L., Liverini, V., Friedli, P. et al. Current quantization in an optically driven electron pump based on self-assembled quantum dots. Nature Phys 7, 423–427 (2011). https://doi.org/10.1038/nphys1918
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DOI: https://doi.org/10.1038/nphys1918
