Study on focused-ion-beam induced site-selective nanoscale luminescence quenching method and its application for high-purity quantum emitters

Abstract

Semiconductor quantum dot-based quantum emitter is physically and chemically stable and shows excellent characteristics in terms of brightness and indistinguishability. Moreover, since it is easy to combine with various optical and electrical devices, it is spotlighted as a core platform for quantum photonic technology. However, in the process of forming quantum dots, unwanted emitters are also frequently generated around the quantum dots, which may reduce the purity of a quantum emitter. In this dissertation, we exploit a technique of site-selective luminescence quenching at unwanted emissions using a focused-ion-beam. The effects of various parameters such as the types of ion and temperatures used in the focused-ion-beam on the crystal structure were analyzed from various angles. Through this technique, the single-photon purity of the quantum dot-based quantum emitter combined with the photonic structure has been improved, and the quantum emitter could be driven even at a relatively high temperature. Furthermore, it was possible to lower the density of luminous quantum dots without destroying the structure of the high-density quantum dots. This enables the combination of single quantum dots and integrated circuits, which was only possible with conventional low-density quantum dots. The focused-ion-beam-based nanoscale quenching technique proposed in this dissertation is expected to open up new possibilities as an ideal quantum emitter for various platforms that were previously limited in terms of single-photon purity.