Nanoscale optical positioning of single quantum dots for bright and pure single-photon emission

Self-assembled, epitaxially-grown InAs/GaAs quantum dots are promising semiconductor quantum emitters that can be integrated on a chip for a variety of photonic quantum information science applications. However, self-assembled growth results in an essentially random in-plane spatial distribution of quantum dots, presenting a challenge in creating devices that exploit the strong interaction of single quantum dots with highly confined optical modes. Here, we present a photoluminescence imaging approach for locating single quantum dots with respect to alignment features with an average position uncertainty < 30 nm (< 10 nm when using a solid immersion lens), which represents an enabling technology for the creation of optimized single quantum dot devices. To that end, we create quantum dot single-photon sources, based on a circular Bragg grating geometry, that simultaneously exhibit high collection efficiency (48 % +/- 5 % into a 0.4 numerical aperture lens, close to the theoretically predicted value of 50 %), low multiphoton probability (g(2)(0) <1 %), and a significant Purcell enhancement factor (~ 3).