title: Terahertz intersublevel transitions in single self-assembled InAs quantum dots with variable electron numbers.
abstract: 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.
authors.affiliation: 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.
authors.forename: Ya
authors.initials: Y
authors.lastname: Zhang
authors.forename: Kenji
authors.initials: K
authors.lastname: Shibata
authors.forename: Naomi
authors.initials: N
authors.lastname: Nagai
authors.forename: Camille
authors.initials: C
authors.lastname: Ndebeka-Bandou
authors.forename: Gerald
authors.initials: G
authors.lastname: Bastard
authors.forename: Kazuhiko
authors.initials: K
authors.lastname: Hirakawa
keywords: Terahertz spectroscopy; intersublevel transitions; nanometer-scale spectroscopy; nanostructures; quantum dots