Radiative lifetimes and linewidth broadening of single InAs quantum dots in an Al_xGa_(1-x)As matrix

We investigate the linewidths and radiative lifetimes of single InAs quantum dots embedded in the ternary matrix AlxGa(1−x)AsAlxGa(1−x)As as a function of aluminum composition. For an increasing aluminum content, we find that the average of the measured linewidths of individual transitions increases. Furthermore, we find that the distribution of the measured linewidths broadens. We infer that the linewidth broadening is the result of spectral wandering caused by inhomogeneities and local defects in the surrounding AlxGa(1−x)AsAlxGa(1−x)As matrix. Local charging and de-charging of defects polarize quantum dots in their vicinity thereby shifting the energy states of the exciton transition in time through the quantum confined Stark effect. The intrinsic radiative lifetimes of numerous quantum dots were determined. We suggest that the observed variation in radiative lifetime at a given photon energy is explained by the influence of an in-plane electric field on the oscillator strength of the electron–hole pair.