Design and growth of metamorphic InAs/InGaAs quantum dots for single photon emission in the telecom window

III-V semiconductor quantum dots are strong candidates for single photon sources and are fundamental cornerstones in the growing field of quantum cryptography and quantum computing. We present an original MBE growth approach, based on the deposition of sub-critical coverages of InAs on metamorphic InGaAs buffers, that allows us to obtain low surface densities for QDs emitting in the 1.3-1.55 mm telecom spectral window. Thanks to the unique properties of the metamorphic system, which allows us to independently change the QD strain and InGaAs buffer composition, we discuss how the sub-critical growth regime is fundamentally different from the widely known Stranski-Krastanow method. Moreover, we present the morphological and optical properties of these nanostructures, aiming to prove that they can be effective single photon sources emitting at 1.3-1.55 mm at low temperatures, thanks to the possibility of engineering the structures by using InGaAs capping layers at different compositions.