High-yield placement of colloidal quantum dot single-photon sources on nanophotonic chips

Spiekermann, Tobias; Eich, Alexander; Gehring, Helge; Sommer, Lisa; Bankwitz, Julian; Pernice, Wolfram; Schuck, Carsten

Abstract

Integrated photonics benefits many quantum technology applications because it allows for replicating crucial circuit components with high yield and high reproducibility. While the integration of single-photon sources with nanophotonic devices has recently been achieved [1], extending the approach to larger numbers of independently controllable emitters has remained challenging. Here we introduce an iterative procedure for site-selective placement of individual colloidal quantum dots (CQD) that provides means for embedding single-photon sources with high yield into photonic integrated circuits at wafer-scale. We lithographically pattern arrays of apertures in polymer thin films, apply CQDs in solution to the sample and remove excess emitters in a lift-off process. We assess emitter placement at aperture positions via confocal microscopy and repeat the process with a modified lithography mask that only contains aperture locations which had remained vacant. This iterative procedure quickly converges towards high-yield and we confirm single-photon emission from predefined sites by recording second-order autocorrelation functions. We further passivate CQD-sites employing atomic layer deposition of alumina (Al2O3), which benefits the emitters photostability.