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Effet d'un champ électrique sur les excitons chargés dans les semi-conducteurs massifs et bidimensionnels

Abstract : The charged excitons result from the binding between an exciton (bound electron-hole pair) and a free electron X- (e,e,h), or a free hole X2+ (e,h,h). We have studied the ground staate of the charged excitons in bulk and bidimenstional semiconductors in the presence of a weak and uniform electric field. In the frame of effective mass approximation, using a simple two bands model, the separation between the center of mass motion and the relative motion stands in the presence of the electric field. The introduction of conditions in the limits of the crystal induces then a quantization of the energy of the center of mass motion. Discrete levels appear then, similar to the "Wannier-Stark" levels, known in the case of an electron in solid. The variational method has been used to solve the Schrödinger equation of the charged exciton in the presence of an electric field. Our results have been compared to H- ion which corresponds to the limit case of X-, when the mass ration [sigma] electron/holes goes to zero. We have studied the stability of the charged exciton X- (3D). Our results show that the electric field enhances the binding energy W. In the case of the bidimensional semiconductor, the binding energies for both types of complexes X- and X2+, increases too. It is shown that charged excitons bound states can exist in 2D semiconductors for larger values of the field than in the 3d case. It is also found that the ration W2D/W3D decreases at increasing fields for all values of the mass ration, the confinement effect becomes then less sensitive
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Abdellatif El Hassani. Effet d'un champ électrique sur les excitons chargés dans les semi-conducteurs massifs et bidimensionnels. Matière Condensée [cond-mat]. Université Paul Verlaine - Metz, 1997. Français. ⟨NNT : 1997METZ054S⟩. ⟨tel-01775909⟩



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