Theory of optically excited intrinsic semiconductor quantum dots

The influence of the Coulomb interaction on one and two electron-hole-pair excitations in semiconductor quantum dots is analyzed. Using a numerical matrix-diagonalization scheme, the energy eigenvalues and the eigenfunctions of the relevant states are computed. Significant deviations from the strong-confinement approximation are observed. It is shown that the biexciton binding energy increases with decreasing dot size. This result is verified using third-order perturbation theory for small quantum dots. The optical properties of the quantum dots are computed, and it is shown that the Coulomb interaction significantly influences the allowed dipole transitions, causing increasing two-pair absorption on the high-energy side of the decreasing one-pair absorption. Surface-polarization effects are studied for quantum dots embedded in another dielectric medium.