C. Riva

Excitons and charged excitons in semiconductor quantum wells

A variational calculation of the ground-state energy of neutral excitons and of positively and negatively charged excitons (trions) confined in a single-quantum well is presented. We study the dependence of the correlation energy and of the binding energy on the well width and on the hole mass. The conditional probability distribution for positively and negatively charged excitons is obtained, providing information on the correlation and the charge distribution in the system. A comparison is made with available experimental data on trion binding energies in GaAs-, ZnSe-, and CdTe-based quantum well structures, which indicates that trions become localized with decreasing quantum well width. (c) 2000 The American Physical Society.

Magnetic field dependence of the energy of negatively charged excitons in semiconductor quantum wells

We present a variational calculation of the spin-singlet and spin-triplet states of a negatively charged exciton (trion) confined to a single quantum well in the presence of a perpendicular magnetic field. We calculated the probability density and the pair correlation function of the singlet and triplet trion states. The dependence of the energy levels and of the binding energy on the well width and on the magnetic field strength was investigated. We compared our results with the available experimental data on GaAs/AlGaAs quantum wells and find that in the low-magnetic-field region (B 25 T) the dark trion becomes optically inactive and possibly a transition to a bright triplet trion (angular momentum L{sub z}=0) state is observed.

Influence of well-width fluctuations on the binding energy of excitons, charged excitons, and biexcitons in GaAs -based quantum wells

We present a first-principle path integral Monte-Carlo (PIMC) study of the binding energy of excitons, trions (positively and negatively charged excitons) and biexcitons bound to single-island interface defects in quasi-two-dimensional GaAs/Al

Off-center D − centers in a quantum well in the presence of a perpendicular magnetic field: Angular-momentum transitions and magnetic evaporation

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Trions in quantum wells

Ga

Positively charged magnetoexcitons in a semiconductor quantum well

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Ground state of excitons and charged excitons in a quantum well

As quantum wells. We discuss in detail the dependence of the binding energy on the size of the well width fluctuations and on the quantum-well width. The numerical results for the well width dependence of the exciton, trions and biexciton binding energy are in good quantitative agreement with the available experimental data.

Binding Energy and Structure of Localized Biexcitons in Quantum Wells

We investigate the effect of the position of the donor in the quantum well on the energy spectrum and the oscillator strength of the D- system in the presence of a perpendicular magnetic field. As a function of the magnetic field we find that when the D- centers are placed sufficiently off-center they undergo singlet-triplet transitions which are similar to those found in many-electron parabolic quantum dots. The main difference is that the number of such transitions depends on the position of the donor and only a finite number of such singlet-triplet transitions are found as function of the strength of the magnetic field. For sufficiently large magnetic fields the two electron system becomes unbound. For the near center D- system no singlet-triplet and no unbinding of the D- is found with increasing magnetic field. A magnetic field vs. donor position phase diagram is presented that depends on the width of the quantum well.

Positively and negatively charged excitons in a semiconductor quantum well

The ground-state energy of three-particle systems consisting of electrons and holes as found in semiconducting quantum wells is studied. The degree of confinement is determined by the quantum-well width and we can vary the dimensionality of the system from two to three dimensions. The energy levels of the system can further be altered by the application of an external magnetic field which is directed perpendicular to the well.

Theory of trions in quantum wells

A variational calculation of the lower singlet and triplet states of positively charged excitons (trions), confined to a single quantum well and in the presence of a perpendicular magnetic field, is presented. All the three particles of the exciton complex are treated within the effective-mass approximation. We study the dependence of the energy levels and of the binding energy on the well width and on the magnetic-field strength. Our results are compared with the available experimental data, and show a good qualitative and quantitative agreement. A singlet-triplet crossing is found which for a