Carrier thermalization within a disordered ensemble of self-assembled quantum dots

The electroluminescence (EL) and photocurrent (PC) spectra of p-i-n structures containing ${\mathrm{In}}_x{\mathrm{Ga}}_{1-x}\mathrm{A}\mathrm{s}/\mathrm{G}\mathrm{a}\mathrm{A}\mathrm{s}$ self-assembled quantum dots (QD’s) are studied from 10 to 290 K. Comparison between the EL and PC shows a Stokes Shift, i.e., the QD emission is redshifted with respect to the QD absorption in PC. The magnitude of the Stokes Shift depends on the temperature and on the extent of the dot energy dispersion, as measured by the QD absorption linewidth in different samples. The origin of the Stokes shift is discussed in terms of carrier thermalization effects by analogy with carrier distribution in disordered quantum wells.