Photoemission spectra for the Cd(0001) surface in the Γ̅-M̅ azimuth were calculated using a multiple scattering method. The emission angle of the photoelectrons θ was kept constant and equal to 35°. The photon energy was varied from 20 eV to 27 eV. The self-consistent potential used in the calculations was generated by the scalar-relativistic LMTO method. A modified image potential for the surface barrier potential was applied. The photoemission spectra show a strong surface state peak at an energy of about 1 eV below the Fermi level.
It is demonstrated that the photoluminescence spectra of single self-assembled quantum dots are very sensitive to the experimental conditions, such as excitation energy and crystal temperature. A qualitative explanation is given in terms of the effective diffusion of the photogenerated carriers, determined by the experimental conditions, which influence the capture probability and hence also the charge state of the quantum dots. This is proposed as a new tool to populate quantum dots with extra electrons in order to study phenomena involving charged excitons.
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