Photoionization cross section and refractive-index change of hydrogenic impurities in a CdS-SiO2 spherical quantum dot

Abstract

Abstract:In this study, we calculate the photoionization cross section and refractive-index change of an on-center hydrogenic impurity in a CdS-SiO 2 spherical quantum dot. In numerical calculations, both the finite-and infinite-confinement cases are considered and a variational scheme is adopted to determine the energy eigenvalues for the impurity. The variations of the photoionization cross section with the dot radius, the refractive-index change, and the normalized photon energy are investigated, and the effect of the potentialbarrier height on the cross section is discussed. The results obtained show that the photoionization cross section and the refractive-index change in CdS-SiO 2 spherical quantum dots are sensitively dependent on the incident optical intensity and on the dot sizes. PACS (2008):

Photoionization cross-section of donor impurity in spherical quantum dots under electric and intense laser fields

“…As is well known the photoionization cross-section (PCS) can be defined as the ionization probability of electrons bound to a hydrogenic impurity under an external optical excitation, and therefore it should be strongly dependent on the confinement profile and its strength as well as on the excitation energies [17]. The PCS describing the transition from the impurity ground-state (as initial state, described by ψ 0 and E 0 ) to the first excited state of the quantum dot without the impurity (as final state, described by ψ 1 and E 1 ) in the dipole and effective mass approximations is given by…”

“…Barseghyan et al [16] have published their results about the hydrostatic pressure and applied electric and magnetic field effects on the impurity binding energy and photoionization cross section in cylindrical quantum dots considering parallel and perpendicular polarizations of the incident radiation. Another group of researchers, Yilmaz et al [17] have calculated the photoionization cross section and refractive index change of an on-center hydrogenic impurity in CdS-SiO 2 spherical quantum dots and their results show a significant dependence on the incident optical intensity and on the dot sizes. The effect of the dielectric mismatch on the photoionization cross section in GaAs quantum dots [19] and in CdSe/ZnS core-shell nanodots under electric fields [20] were studied by Niculescu et al Though the first studies on effects of high-frequency intense laser field on quantum systems dates back about 30 years [21,22], the interaction of carriers with electromagnetic radiation, proper to optoelectronic devices based on heterostructures, maintains this domain in the researcher attention.…”

“…The photoionization cross section of a hydrogenic impurity in low-dimensional structures was studied by many authors [13][14][15][16][17][18][19][20].…”

Photoionization cross section in a spherical quantum dot: Effects of some parabolic confining electric potentials

“…In this regard, photoionization studies on nanostructures could offer an insight into the electron-impurity interaction in a wide variety of conditions. As such, the literature is awash with investigations of PCS [11][12][13][14][15].…”