Abstract-Terahertz Intersublevel Transitions in Single Self-Assembled InAs Quantum Dots with Variable Electron Numbers

Ya Zhang *†, Kenji Shibata †‡, Naomi Nagai †, Camille Ndebeka-Bandou †§, Gerald Bastard †§, and Kazuhiko Hirakawa *†‡

†Center for Photonics Electronics Convergence, Institute of Industrial Science and ‡Institute for Nano Quantum Information Electronics, University of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo 153-8505, Japan

§ Laboratoire Pierre Aigrain, Ecole Normale Superieure, 24 rue Lhomond F75005, Paris, France

Nano Lett., Article ASAP

DOI: 10.1021/nl5042319

Publication Date (Web): January 12, 2015

Copyright © 2015 American Chemical Society

http://pubs.acs.org/doi/abs/10.1021/nl5042319

We propose a method for performing terahertz spectroscopy on nanometer (nm)-scale systems by using metal nanogap electrodes. Intersublevel transition spectra of single self-assembled InAs quantum dots (QDs) have been measured with high signal/noise ratios by using a single electron transistor geometry that consists of a QD and nanogap metal electrodes as a terahertz detector. Photocurrent distribution with respect to the Coulomb diamonds indicates that there are two mechanisms for the photocurrent generation. When the p shell was fully occupied, we observed rather simple photocurrent spectra induced by the p → d transitions. However, when the p shell was half-filled, the photocurrent spectra exhibited a markedly different behavior, which we attribute to the fluctuation in electron configuration when the empty p state is filled back from the electrodes.

Keywords: 

Terahertz spectroscopy; nanostructures; intersublevel transitions; quantum dots; nanometer-scale spectroscopy