Structure parameters and external electric field effects on exciton binding energies of CdTe/ZnTe quantum dots

We study the effects of the structure parameters of self-assembled CdTe/ZnTe quantum dots (QDs) under an electric field on the exciton binding energies due to Coulomb interaction between electrons and holes with a finite-element method based on the linear elasticity theory of solids and the eight-band k · p Hamiltonian. The exciton binding energy is shown to decrease with increasing base width of the QD, regardless of its height. We point out that the monotonic decrease in the exciton binding energy is due to the confinement of the electron and the hole wavefunctions inside the QD. The exciton binding energy is also found to decrease as the wetting layer thickness increases, which can be attributed to the dipole-like wavefunction of the hole. The fact that the electron and the hole energies decrease parabolically and the exciton binding energy decreases with increasing electric field due to the Stark effect is demonstrated.