Vanishing fine structure splittings in telecom wavelength quantum dots\n grown on (111)A surfaces by droplet epitaxy

Abstract

The emission cascade of a single quantum dot is a promising source of\nentangled photons. A prerequisite for this source is the use of a symmetric dot\nanalogous to an atom in a vacuum, but the simultaneous achievement of\nstructural symmetry and emission in a telecom band poses a challenge. Here we\nreport the growth and characterization of highly symmetric InAs/InAlAs quantum\ndots self-assembled on C3v symmetric InP(111)A. The broad emission spectra\ncover the O (1.3 micron-m), C (1.55 micron-m), and L (1.6 micron-m) telecom\nbands. The distribution of the fine-structure splittings is considerably\nsmaller than those reported in previous works on dots at similar wavelengths.\nThe presence of dots with degenerate exciton lines is further confirmed by the\noptical orientation technique. Thus, our dot systems are expected to serve as\nefficient entangled photon emitters for long-distance fiber-based quantum key\ndistribution.\n