Origin of Stokes shift in InAs and CdSe quantum dots: Exchange splitting of excitonic states

The mechanism of Stokes shift in semiconductor quantum dots is investigated by calculating the energy of the excitonic states. We have taken into account all possible contributions to the total electronic energy in the dot---i.e., the dielectric mismatch between the dot and surrounding medium, the effects of finite barrier height, and the electron-hole exchange interaction. The Stokes shift is calculated as a function of radius of dot and compared with experimental data on two different semiconductor based quantum dots. These results provide evidence for an exchange splitting of excitonic states, as the mechanism of Stokes shift in quantum dots.