Geometrical-confinement effects on excitons in quantum disks

Abstract

Excitons confined to flat semiconductor quantum dots with elliptical cross section are considered as we study geometrical effects on exciton binding energy, electron-hole separation, and the resulting linear optical properties. We use numerical matrix diagonalization techniques with appropriately large and optimized basis sets in an effective-mass Hamiltonian approach. The linear optical susceptibilities of GaAs and InAs dots for several different size ratios are discussed and compared to experimental photoluminescence spectra obtained on GaAs/AlGaAs and InAs/GaAs quantum dots. For quantum dots with several nm in size, there is a strong blue shift of the luminescence due to geometrical confinement effects. Also, transition peaks are split and shifted towards higher energy, in comparison with dots with circular cross sections.