Effect of Correlation and Dielectric Confinement on 1S1/2(e)nS3/2(h) Excitons in CdTe/CdSe and CdSe/CdTe Type-II Quantum Dots

We calculate correlated exciton states in type-II core/shell quantum dots (QDs) using a configuration interaction method combined with the k·p theory. We map the 1S1/2(e)1S3/2(h) and 1S1/2(e)2S3/2(h) exciton correlation energy relative to the strong confinement approximation as a function of core radius, shell thickness, and dielectric confinement. The type-II confinement potentials enhance the effect of dielectric confinement which can significantly affect the wave functions and exciton energies in such heterostructures. Dielectric confinement mainly increases the correlation energy for QDs in which the corresponding single-particle hole states are delocalized. We also find that correlation leads to large changes in the optical dipole matrix element, particularly for the lowest CdSe/CdTe QD exciton, in the presence of dielectric confinement. We conclude that dielectric confinement affected the exciton properties in CdSe/CdTe QDs more than in CdTe/CdSe QDs due to the band alignment which encourages holes ...