  The GaAs-based material system is well-known for the implementation of InAs
quantum dots (QDs) with outstanding optical properties. However, these dots
typically emit at a wavelength of around 900nm. The insertion of a metamorphic
buffer (MMB) can shift the emission to the technologically attractive telecom
C-band range centered at 1550nm. However, the thickness of common MMB designs
limits their compatibility with most photonic resonator types. Here we report
on the MOVPE growth of a novel InGaAs MMB with a non-linear indium content
grading profile designed to maximize plastic relaxation within minimal layer
thickness. Single-photon emission at 1550nm from InAs QDs deposited on top of
this thin-film MMB is demonstrated. The strength of the new design is proven by
integrating it into a bullseye cavity via nano-structuring techniques. The
presented advances in the epitaxial growth of QD/MMB structures form the basis
for the fabrication of high-quality telecom non-classical light sources as a
key component of photonic quantum technologies.
