Modelling of metamorphic quantum dots for single photon generation at long wavelength

In this work we present the modelling of In_xGa_1-xAs/In_zGa_1-zAs/In_yGa_1-yAs metamorphic quantum dot nanostructures. These are of great recent interest as the active materials in single photon devices emitting in the telecom windows. We have calculated: (i) strain-dependent energy band profiles, (ii) ground energy levels for electrons and heavy holes, (iii) carrier probability densities and (iv) oscillation strenghts for radiative recombination for structures where the In composition in the metamorphic buffer x and in the cap layer y were varied. The modelization has been carried out using the TiberCAD software on the basis of realistic parameters and results have been compared against experimental photoluminescence data: such a comparison shows that the calculated and experimental values agree within a 10 meV interval. Simulations show that in the metamorphic quantum dot (QD) system, a Type-II quantum confinement regime can occurr for particular values of x and y, a feature not reported so far for In(Ga)As QDs. Furthermore, we have been able to identify an optimized design for 10 K light emission at 1.55 μm with the highest emission efficiency. These results will be useful to improve the design and the preparation of QD nanostructures for single photon emission in the telecom windows, a topic of high relevance for the upcoming quantum technology revolution.