Piezoelectric InAs/GaAs quantum dots with reduced fine-structure splitting for the generation of entangled photons

Abstract

Polarization-resolved single-dot spectroscopy reveals that the exciton fine-structure splitting in piezoelectric (211)B InAs/GaAs quantum dots is smaller than 10 \ensuremath{\mu}eV in the vast majority of examined dots. These values are significantly reduced compared to as-grown (100)-oriented InAs dots. Time-resolved measurements confirm the high oscillator strength of these dots, in spite of the internal piezoelectric field, suggesting good quantum efficiency at 4 K, comparable with that of (100) InAs/GaAs dots. Lastly, photon correlation measurements demonstrate single-photon emission from exciton levels of these dots. All these features make this intriguing dot system promising for implementing solid-state entangled photon sources.