The Photoionization Cross-Section of Impurities in Quantum Dots

Abstract

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.

Linear and nonlinear optical absorption coefficients of two-electron spherical quantum dot with parabolic potential

“…The linear, the second-and the third-order nonlinear optical susceptibilities are labeled by the terms χ ω ( ) (1) , χ ω (2 ) (2) and χ ω (3 ) (3) , respectively, and ε 0 is the electrical permittivity of the vacuum. Since our system is spherical symmetric, the term χ ω (2 ) (2) is not taken into account.…”

“…Confined quantum systems have been one of the most important subjects of investigation. Therefore, due to their fundamental properties and their wide range of technological applications [1], a great deal of theoretical works on these structures has been reported extensively by using different methods like a finite element method [2,3], perturbation [4], density functional [5,6], configuration interaction [7,8], variational [9,10], exact solution [11], quantum genetic algorithm and Hartree-Fock Roothaan method [12] and other methods [13,14]. Understanding of the electronic and optical properties in such structures is important because these properties are strongly affected by the presence of impurity.…”

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

“…In order for such a transition to occur, the excitation energy should be greater than the photoionization threshold energy E . As known from the literature, the photon energies involved in a photoionization process in small quantum dots (QDs) are generally larger than those for quantum wells (QWs) or quantumwell wires (QWWs) systems [34]. The main reason for this is the increase in the confinement of the electrons and thus the enhancement of the optical photoionization threshold energies.…”

“…In addition to the above mentioned studies, the spectral dependence of the photoionization cross section in quantum box structures has been analyzed in Ref. [34]. Ham et al [35] have investigated the photoionization in a cylindrical quantum wire using an infinite-well model.…”

Photoionization cross-section and binding energy of donor impurities in GaAs, Ge and Si quantum wires with infinite barriers

“…The excitation energy dependence of the photoionization cross-section associated with an impurity, starting from Fermi's golden rule in the well-known dipole approximation, as in the bulk case is [2,6,[12][13][14] …”