Cavity-enhanced emission in electrically driven quantum dot single-photon-emitters

Abstract

Efficient generation of polarized single photons or entangled photon pairs is a crucial requirement for the implementation of quantum key distribution (QKD) systems [1] [2]. In this context, self-organized semiconductor quantum dots (QDs) [3] [4] play a decisive role as they are capable of emitting only one polarized photon at a time using appropriate electrical current injection [5] [6]. Therefore, a single QD embedded in a LED can be used as a single photon source. By tuning the electronic structure it is possible to use QD as source for entangled photons. Resonant cavity-induced enhancement of spontaneous emission and out-coupling efficiency can improve external quantum efficiency of quantum dot based single photon sources dramatically. In order to optimise the device geometry detailed numerical device modelling must be performed. The modelling of the electromagnetic field were done using eigenmode-techniques. The essential design parameters, such as cavity length, aperture diameter, position and thickness were systematically varied. We designed and fabricated optimized resonant cavity light emitting diodes combined with a submicron oxide current aperture, to pump individual InGaAs/GaAs QDs electrically. These devices demonstrates more than ten times increased single photon rate in comparison to the simple LED design. Pulsed correlation measurements demonstrated true single photon emission with g2(0) = 0 at a rate of 1 GHz.