Resonant excitation study of ultrasharp emission lines in ordered ${\mathrm{Ga}}_x{\mathrm{In}}_{1-x}\mathrm{P}$

Narrow-line photoluminescence in the below-gap spectral region of ordered ${\mathrm{Ga}}_x{\mathrm{In}}_{1-x}\mathrm{P}$ is investigated with high-spatial and -spectral resolution photoluminescence excitation and time-resolved spectroscopy. Sharp absorption lines are found both correlated and uncorrelated with emission lines, indicating multiple coupled systems. Saturation and temporal measurements support a quantum dot model.