Photoionization of impurities in quantum wells

The Photoionization Cross-Section of Impurities in Quantum Dots

“…These interesting results which are characteristic of a small dot are not exhibited in quantum well and quantum-well wire structures in which the observed transitions were strongly dependent on the polarization of the exciting light. More precisely, the same behaviour is exhibited in quantum wells [55] and quantum-well wires [60] when the direction of the incident light polarization is parallel to the confinement axis of the well and to the two directions of the confinement of the 216 A. Sali et al: The Photoionization Cross-Section of Impurities in Quantum Dots Fig. 1.…”

“…The photon energy dependence of the photoionization cross-section in low-dimensional electronic systems is generally determined by the impurity ground state wavefunction, the potential which links the electron to the donor impurity and the conduction subband of the host crystal and by the wavefunction of the conduction subbands into which the charge carrier is excited. Recently, much attention has been devoted to the study of the hydrogenic impurity photoionization cross-section in systems with reduced dimensionality such as quantum wells [53][54][55][56][57][58] and quantum-well wires [59][60][61]. Most of these works can be summarized as follows: Takikawa et al [53] have experimentally and theoretically examined the photoionization of the deep traps in AlGaAs/GaAs multiple quantum well layers grown by metalorganic chemical vapour deposition.…”

“…El-Said and Tomak [54] have investigated the dependence of the photoionization crosssection on photon energy for shallow donors in infinite-barrier GaAs/Ga 1Àx Al x As quantum wells for incident light polarization assumed in the x-direction. The same work as before has been done for light polarized in the z-direction by considering optical transitions that take place from the impurity ground state as the initial state to the second subband as the final continuum state [55]. Moreover, the spectral dependence of the photoionization cross-section on photon energy for shallow donor impurities in a finitebarrier quantum well and for incident light polarized along the z-axis of the well has been studied [56].…”

The effects of temperature and hydrostatic pressure on the photoionization cross-section and binding energy of impurities in quantum-well wires

“…Lax [1] first investigated the photoionization cross-section of hydrogenic impurities in bulk semiconductors. In recent years, work has been done on the photoionization crosssection of hydrogenic impurities in dimensionally reduced structures such as quantum wells, wires and quantum dots [2][3][4][5][6][7][8][9][10]. It has been found that greater the confinement in such low-dimensional structures, greater the binding energy of these hydrogenic impurities.…”

“…Takikawa et al [2] have theoretically and experimentally examined the photoionization cross-section associated with a transition from a deep trap to subbands. El-Said and Tomak [3,4] have investigated the photon energy dependence of the photoionization cross-section of hydrogenic impurities using the infinite barrier model. They found out that the photoionization cross-section depended upon the polarization of the incident light relative to the direction of the carrier confinement.…”