From localization to quantum-dot chains in self-formed core-shell InGaN nanowires emitting in the red

Self-formed core-shell InGaN nanowires (NWs) grown by plasma-assisted molecular beam epitaxy on p-Si (111) are studied by temperature-dependent and time-resolved photoluminescence (PL) spectroscopy. Clear localization and associated photocarrier redistribution can be evidenced by the S-shape temperature dependence of the PL peak energy and inflection of the PL linewidth. An unexpected maximum of the integrated PL intensity as a function of temperature is observed. This maximum is identified as proof that the localized states behave as chains of quantum dots with reduced radiative lifetime due to the combination of strong two-dimensional lateral quantum confinement in the NW core with localization. This is underlined by the time-resolved PL measurements exhibiting a fast, sub-ns, single-exponential decay, in addition evidencing negligible quantum-confined Stark effect for efficient light sources emitting in the red.