Spectral diffusion of single InP/GaxIn1-xP quantum dot luminescence

Abstract

High spatial resolution photoluminescence spectroscopy of single self-assembled InP quantum dots in a Ga0.5In0.5P matrix reveal an abrupt change from the common but yet unclear broad emission band at low temperatures to narrow lines at T greater than or equal to 45 K. The emission into narrow lines even at higher temperatures is the expected behaviour for a fully confined quantum system. The spectrally broad emission (several meV) from individual quantum dots at low temperatures is explained by fluctuating charge configurations surrounding the quantum dot and causing spectral diffusion of the transition energies via the quantum-confined Stark effect. The interacting charges are trapped by thickness variations in the surrounding wetting layer. At higher temperatures these traps are depleted due to the shift of the Fermi level E-F below the energy of the corresponding states in the wetting layer.