Arsenic/phosphorus exchange and wavelength tuning of in situ annealed InAs/InP quantum dot superlattice

We report the solid-source molecular beam epitaxial (SSMBE) growth of InAs/InP quantum dots (QDs) superlattices and the effect of As/P exchange. The InAs QDs were found to have an average lateral diameter of ∼40 nm and density of 3 to 4×1010 cm−2. The single-layer QDs have photoluminescence (PL) emission centred at 0.78 eV with a linewidth of 64 meV at low temperature (4 K). Double-crystal X-ray diffraction (DCXRD) spectra showed evidence of significant As/P exchange during in situ annealing under P2 pressure before growing the spacer layer. An average P composition of ∼30% in the resulting InAsP QDs in samples annealed for 50 s was deduced from dynamical simulations of the experimental DCXRD spectra. The QDs superlattice PL emission exhibits a blueshift with increase of annealing time, and emission at 1.55 μm at 300 K was achieved. This observation holds promise for possible telecommunication device applications at long wavelength.