Electrically driven single photon sources based on single quantum dot RCLEDs

Abstract

Self-organized quantum dots (QDs) demonstrated recently their excellent capability for compact electrically driven single and entangled photon sources [1]. Electrical pumping of single QDs embedded in pin-diode structures poses two main challenges: The first is the control of the current path in a way that only one QD is pumped, and the second is to assure that the QD is equally filled by electrons and holes to achieve emission from uncharged excitons. Thus the uncharged biexciton-exciton decay cascade can be used for the creation of entangled photon pairs (provided the fine-structure splitting (FSS) is small enough) or single polarized photons (for large FSS), prerequisite for the BB84 protocol. The second key specification of single photon sources for the realization of a quantum cryptography system is a high repetition rate and a low fraction of empty pulses. The repetition rate in QD based single photon sources is limited by the exciton life time and the parasitic electrical bandwidth of the device, whereas the number of empty pulses is mainly controlled by the out-coupling efficiency.