Droplet epitaxy InAs/InP quantum dots in etched pits for single photon emitters at 1550 nm: morphology, optical and electronic properties, and etching kinetics.

We utilize a droplet epitaxy scheme to fabricate low surface density (2.8$\times$10$^8$ cm$^{-2}$) InAs quantum dots on an (001)InP substrate with nearly symmetric quantum confinement potential, emitting at the third telecom window. We show that the local etching of the In droplet results in the formation of nearly-symmetric QDs with an arch-shaped base and we explain the QD growth kinetics by the atom diffusion model. Electronic band structure calculations reveal properties of neutral and charged excitons confined in the dots, including respective emission and binding energies. These values are confirmed in the high-spatially-resolved photoluminescence experiment. We show that the quantum dots can be considered as non-classical photon emitters with a high single-photon emission purity at $\sim$1500 nm.