Abstract
We report on the realization of an array of 28 × 28 mesas with site-controlled InGaAs quantum dots acting as single-photon sources for potential applications in photonic quantum technology. The site-selective growth of quantum dots is achieved by using the buried stressor approach where an oxide aperture serves as the nucleation site in the center of each mesa. Spectroscopic maps demonstrate the positioning of quantum dots with an inhomogeneous broadening of the ensemble emission of only 15.8 meV. Individual quantum dots are characterized by clean single-quantum-dot spectra with narrow exciton, biexciton, and trion lines, with a best value of 27 μeV and an ensemble average of 120 μeV. Beyond that, Hanbury Brown and Twiss and Hong-Ou-Mandel measurements validate the quantum nature of emission in terms of high single-photon purity and photon indistinguishability with a g(2)(0) value of (0.026 ± 0.026) and a post-selected two-photon interference visibility V = (87.1 ± 9.7)% with an associated coherence time of τc = (194 ± 7) ps.
Highlights
Quantum devices based on self-assembled semiconductor quantum dots (QDs) are promising building blocks for applications in photonic quantum technology
We demonstrate that the buried stressor approach is an attractive method to realize arrays of site-controlled InGaAs
Photon statistics measured in Hanbury Brown and Twiss (HBT)- and HOM-type experiments confirm strong multi-photon suppression with a fitted value of gd(e2c)onv(0) = 0.026 ± 0.026 and bility expressed in a deconvoluted high post-selected visibility of Vdeconv indistinguisha= (87.1 ± 9.7)%
Summary
Quantum devices based on self-assembled semiconductor quantum dots (QDs) are promising building blocks for applications in photonic quantum technology. Until now, these quantum emitters have been studied mainly regarding their fundamental optical properties in proof-of-principle experiments, in which they showed close-to-ideal characteristics in terms of on-demand emission of indistinguishable photons and entangled photon pairs with small emission linewidths. More recently, the application relevance of QD-based single-photon sources (SPS) has been demonstrated by developing fiber-coupled stand-alone devices.. These devices still rely on integrating self-assembled QDs with random position limiting the scalability of this approach To overcome these issues, the site-controlled growth of QDs is highly attractive as it allows for realizing arrays of single-photon emitters for large-scale device integration and systems with high quantum functionality. The QDs are in close proximity to defects at the etched surface of the nano-holes leading to moderate quantum efficiency and pronounced inhomogeneous broadening of single-QD emission lines even in stacked layers of site-controlled quantum dots (SCQDs).28,30 This problem can be mediated by introducing thicker buffer layers between the nanoholes and the SCQDs, at the cost of a lower occupation probability of the pre-defined sites.. The oxide aperture is similar to the ones used in vertical-cavity surface-emitting lasers and allows for efficient carrier injection via self-aligned upper contacts.
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