Telecom-wavelength (1.5 μm) single-photon emission from InP-based quantum dots

We demonstrate pronounced single-photon emission from InAs/AlGaInAs/InP quantum dots (QDs) at wavelengths above 1.5 μm that are compatible with standard long-distance fiber communication. The QDs are grown by molecular beam epitaxy on distributed Bragg reflectors. A low QD density of about 5 × 10⁸ cm⁻² was obtained using optimized growth conditions. Low-temperature micro-photoluminescence spectroscopy exhibits sharp excitonic emission lines from single QDs without the necessity of further processing steps. The combination of excitation power-dependent and polarization-resolved photoluminescence measurements reveal a characteristic exciton-biexciton behavior with biexciton binding energies that range from 3.5 to 4 meV and fine-structure splitting values down to 20 μeV.