A High Efficiency, Purcell-enhanced Microcavity Single Photon Emitting Diode
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1208-O03-04
A High Efficiency, Purcell-enhanced Microcavity Single Photon Emitting Diode.
D. J. P. Ellis1, A. J. Bennett1, S. J. Dewhurst1,2, C. A. Nicoll2, D. A. Ritchie2, A. J. Shields1 1
Toshiba Research Europe Ltd, 208 Cambridge Science Park, Milton Road, Cambridge, CB4 0GZ, U.K. 2 Cavendish Laboratory, University of Cambridge, J. J. Thomson Avenue, Cambridge, CB3 0HE, U.K. ABSTRACT Efficient, high-frequency quantum light sources are a prerequisite for advanced quantum information processing. Here, we report the observation of a Purcell enhancement in the radiative decay rate of a single quantum dot, embedded in a microcavity light-emitting diode structure. An annulus of low-refractive-index aluminium oxide, formed by wet oxidation, is used to simultaneously achieve lateral confinement of both the optical mode and the current through the device. This technique reduces the active area of the device without impeding the electrical properties of the p-i-n diode. We measure a photon collection efficiency of 14 ± 1% and demonstrate single photon electroluminescence at repetition rates up to 0.5 GHz.
INTRODUCTION Semiconductor quantum dots (QDs) are widely regarded as ideal candidates for use as the active element in such single-photon emitters: they are able to confine both electrons and holes in small numbers and, when the carriers recombine, they produce a series of sharp emission features – characterized by the combination of carriers confined within the dot [1]. QDs also emit antibunched photons, that is to say that the emission statistics show a reduced probability of the simultaneous emission of more than one photon from a particular state. When embedded in GaAs, self-assembled InAs QDs may be excited optically by means of a pump laser that is focussed onto the sample or, if the quantum dots are embedded in a p-i-n diode structure, they may be electrically excited [2]. For a practical source, electrical injection is particularly favourable as it eliminates the necessity for a pump laser and associated optics. Quantum dots alone are not, however, the whole solution. If a quantum dot is embedded in bulk GaAs, total internal reflection at the air–GaAs interface dramatically reduces the fraction of emitted photons that can escape from the crystal. If an objective lens of numerical aperture (NA) 0.5 is then used to collect the emission, it can be shown that, at most, only 0.5% of the emitted photons could be coupled into an experiment [3]. It is well known that embedding the quantum dots in a microcavity structure can increase the efficiency with which the photons are collected [4]. Furthermore coupling the QD emission to a confined cavity mode also provides a route to control the radiative dynamics of the source through the Purcell effect. This is of
particular importance for guaranteeing indistinguishable photons [5] and realizing high repetition rate devices. Here we report the successful integration of a high quality optical cavity with an electrically small p-i-n single-photon-emitting diode [6]. This com
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