PACS: 71.55.Eq; 73.21.La In quantum dot structures, photoionization has been considered as an optical transition from the impurity ground state to the conduction subbands. Using a variational approach, we have calculated the photon energy dependence of the photoionization cross-section for a hydrogenic donor impurity in an infinite barrier GaAs quantum dot as a function of the sizes of the dot and the impurity position. The results we have obtained show that the photoionization cross-section is strongly affected by the quantum size effects and the position of the impurity and its overall shape seems to be a signature of the quantum dot system.

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The effect of a strong magnetic field on the binding energy and the photon energy dependence of the photoionization cross-section as a function of the well size is studied in a quantum well for several values of the magnetic field, taking into account the finite character of the barrier potential. The results we have obtained show that the applied strong magnetic field affects drastically the binding energy and the photoionization cross-section and this effect is more significant in a quasi-two-dimensional structure than in a three-dimensional system.