Temperature-dependent linewidth of single InP/GaxIn1-xP quantum dots: Interaction with surrounding charge configurations

We have investigated individual metal-organic vapor phase epitaxy-grown sel f-assembled InP quantum-dots in a Ga0.5In0.5P matrix by means of photolumin escence with high spatial resolution as a function of temperature and excit ation density. We observe an abrupt change from the well-known but yet uncl ear relatively broad emission band at low temperatures to narrow lines at T greater than or equal to 45 K. The high-temperature mode is the one expect ed for a fully confined quantum system. The ubiquitous broadening at low te mperature is discussed in the framework of spectral diffusion, i.e., fluctu ating charge configurations surrounding the quantum dot influence its trans ition energies. We conclude that the interacting charges are most probably trapped in connection with thickness variation in the wetting,a layer. Thei r release at higher temperatures removes the perturbation and leads to the expected appearance of sharp single dot spectra.