Exciton Fine Structure in InAs Quantum Dots with Cavity-Enhanced Emission at Telecommunication Wavelength and Grown on a GaAs (111) A Vicinal Substrate

The efficient generation of entangled photons at telecom wavelength is essential for the success of many quantum communication protocols and the development of fiber-based quantum networks. Entangled light can be generated by solid-state quantum emitters with naturally low fine-structure splitting, such as highly symmetric InAs quantum dots (QDs) grown on (111)-oriented surfaces. The incorporation of these QDs into optical cavities is crucial to achieve sufficient signal intensities for applications but has so far shown major complications. In this work, we present droplet epitaxy of telecom-wavelength InAs QDs within an optical cavity on a vicinal (2° miscut) GaAs(111)A substrate. We show a remarkable enhancement of the photon extraction efficiency compared to previous reports together with a reduction of the density that facilitates the isolation of single spectral lines. Moreover, we characterize the exciton-fine-structure splitting and employ numerical simulations under the framework of the empirical-pseudopotential and configuration-interaction methods to study the impact of the miscut on the optical properties of the QDs. We demonstrate that the presence of the miscut steps influences the polarization of the neutral excitons and introduces a preferential orientation in the C3v symmetry of the surface.