Contents 1. Introduction
The realization of efficient single photon sources (SPS) is motivated by a possible application of these devices in quantum communication systems. Many SPS-approaches are based on single QDs that inherently act as single photon emitters due to their discrete energy level system. However, QDs suffer from a pure out-coupling efficiency when embedded in a bulk semiconductor matrix due to total internal reflection. The efficiency of a QD based SPS is strongly enhanced in combination with high quality microcavities [1], [2]. In this respect QD-micropillar cavities are very attractive systems due to a high extraction efficiency approaching 70% as predicted by theory and a highly directional emission normal to the sample surface [3]. While most QD-SPS rely on optical pumping by an external laser source a practical devices should be electrically driven. Up to now only a few approaches for electrically pumped SPS based on QDs embedded in oxide aperture pin-diodes with and without cavity effects and an efficiency of up to 14% have been demonstrated [4]. Here, we will present highly efficient single photon emission from electrically driven QD-micropillar cavities. We will report on record high single photon emission rates as high as 35 MHz and an extraction efficiency of up to 34%. (a) Scanning electron microscope image showing the cross section of a fully processed electrically contacted micropillar cavity with a diameter of 2.0 . (b) EL intensity map showing the temperature tuning of a single negatively charged QD exciton into resonance with the fundamental mode (C) of a 2.0 diameter micropillar under pulsed excitation at 220 MHz.
