Universality of the Stokes shift for a disordered ensemble of quantum dots

We present a study of carrier redistribution in InxGa1-xAs/GaAs self-assemb led quantum dots (QDs) by comparing electroluminescence (EL) and photocurre nt (PC) spectra. We show the: existence of a red-shift of the dot emission in EL relative to the dot absorption in PC, referred to as the Stokes shift (SS). The existence of the SS is explained in terms of a thermal redistrib ution of carriers between dots. According to the thermalization model, the SS increases with the linewidth of the QD absorption spectrum. We show that for a large variety of quantum dots, differing in the material system and/ or the growth technique, the SS has a universal dependence on the QD absorp tion linewidth.