4 research outputs found
Size dependence of the polarizability and Haynes rule for an exciton bound to an ionized donor in a single spherical quantum dot
International audienceWe study the effect of an external electric field on an exciton bound to an ionized donor (D+, X) confined in a spherical quantum dot using a perturbative-variational method where the wave function and energy are developed in series of powers of the electric field strength. After testing this new approach in the determination of the band gap for some semiconductor materials, we generalize it to the case of (D+, X) in the presence of the electric field and for several materials ZnO, PbSe, and InAs, with significant values of the mass ratio. Three interesting results can be deduced: First, we show that the present method allows to determine the ground state energy in the presence of a weak electric field in a simple way (E = E-0 - alpha f(2)) using the energy without electric field E-0 and the polarizability a. The second point is that our theoretical predictions show that the polarizability of (D+, X) varies proportionally to R-3.5 and follows an ordering alpha(D0) < alpha(X) < alpha((D+, X)). The last point to highlight is that the Haynes rule remains valid even in the presence of a weak electric field
Diamagnetic susceptibility of bound exciton in cylindrical quantum nanodots under hydrostatic pressure and temperature effects
Stark shift and dissociation process of an ionized donor bound exciton in spherical quantum dots
The effect of an electric field on the ground state energy of an exciton bound to an ionized donor (D+, X) was studied in CdSe spherical quantum dots where quantum confinement is described by an infinitly deep potential. Calculations have been performed in the framework of the effective mass approximation using a variational method by choosing an appropriate sixty-terms wave function taking into account different interparticles correlations and symetry distorsion induced by the electric field. It appears that the Stark shift is significant even for low fields and depends strongly of spherical dot sizes. The competition between the confinement effect and the Stark effect is discussed as function of the spherical dot size and the applied electric field strength. The (D+, X) Stark shift is estimated and its behavior is discussed as a function of the dot radius and electric field strength. The electron and hole average distances have also been calculated and the role of the ionized donor in the excitonic dissociation is established