Semiconductor quantum dots (QDs) have attracted persistent attention due to their plethora of possible applications including, not at last, the generation of cascaded and entangled photon pairs. The concept of entanglement can be utilized in quantum cryptography schemes or quantum repeaters, where solid-state based non-classical light sources constitute a feasible straightforward device implementation due to their high integrability. InGaAs QDs embedded in a GaAs matrix play an important role in that regard offering high extraction efficiencies through photonic cavities and site-controlled growth. Besides the generation of entanglement, not only the generation of indistinguishable photons has been shown but also the QDs’ emission wavelengths can be tuned over a wide spectral range. Communication networks on the basis of glass fiber technology mainly rely on transmission in the telecom wavelength bands at 1.31 µm (O-band) and 1.55 µm (C-band), corresponding to the dispersion and absorption minima. By applying an InGaAs strain reducing layer (SRL), the emission wavelengths of InGaAs QDs can be precisely shifted to the telecom O-band.
By metal-organic vapor-phase epitaxy, we have fabricated InGaAs quantum dots on GaAs substrate with an ultra-low lateral density (<10 7 cm 2). The photoluminescence emission from the quantum dots is shifted to the telecom O-band at 1.31 µm by an InGaAs strain reducing layer. In time-resolved measurements, we find fast decay times for exciton (600 ps) and biexciton (300 ps). We demonstrate triggered single-photon emission (g (2)(0)= 0.08) as well as cascaded emission from the biexciton decay. Our results suggest that these quantum dots can compete with their counterparts grown by state-of-the-art-molecular beam epitaxy.
Publication: Metal-organic vapor-phase epitaxy-grown ultra-low density InGaAs/GaAs quantum dots exhibiting cascaded single-photon emission at 1.3 µm
Matthias Paul, Jan Kettler, Katharina Zeuner, Caterina Clausen, Michael Jetter and Peter Michler 
Publication: Appl. Phys. Lett. 106, 122105 (2015)
Contact person: S. Hepp