Interfacial compositional disordering in In 0.6 Ga 0.4 A s/G a A s quantum dots has been used to tune their intersublevel energy spacings (Δ E [(i+ 1)− i]). Interdiffusion blueshifted all levels while lowering values for Δ E [(i+ 1)− i]. Rate equation simulations of photoluminescence (PL) spectra estimated relaxation lifetime ratios for intersublevel transitions. A slight trend towards increasing thermalization rates at values Δ E [(i+ 1)− i]∼ LO phonon energies was found. However, PL measurements showed strong emission from excited states for all Δ E [(i+ 1)− i] values, which ranged from 53 to 25 meV.