Positively charged magnetoexcitons in a semiconductor quantum well

Abstract

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. 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 200Å wide GaAs is predicted to occur for B= 15 T.

Relative stability of negative and positive trions in model symmetric quantum wires

“…8. This crossing is qualitatively opposite to the one obtained for two-dimensional quantum wells, 13 in which a small magnetic field ͑around 1 T͒ increased the X − stability over the X + binding energy. In quantum wells the magnetic-field related increase of the single-particle energy is smaller for electrons and holes bound in the trion complex than for the lowest Landau level in the final state of the free electron and hole after the trion dissociation.…”

“…2 of Ref. 13. In the present calculations the free electron and the free hole are strongly localized in the plane perpendicular to the field and the single-particle magnetic field effects cancel due to the assumption of the frozen-lateral degrees of freedom, so that the crossing is entirely due to the modified effective interparticle interactions.…”

“…The magnetic field perpendicular to the plane of confinement enhances more strongly the X − stability leading to a crossing of X − and X + binding energies. 13,14 For trions localized on a defect of the quantum well potential X − can become more stable than X + even without the presence of an external magnetic field. 15 The combined quantum well and defect confinement creates a three-dimensional potential similar to a quantum dot.…”

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

“…For example, both in Ref. [30] and Ref. [16] it was found that the X + binding energy is larger by about 20% than the X − binding energy.…”

Magneto-optical probing of weak disorder in a two-dimensional hole gas

“…The three-body dynamics of a trion might at first sight seem analogous to the familiar Hydrogen ion problem. However, comparable e and h masses, confinement, magnetic field, nonparabolic and anisotropic hole dispersion, and coupling to the crystal lattice, surrounding carriers, or impurities -all generate complexity making trions fascinating objects of intense experimental [15,16,17,18,19,20] and theoretical [21,22,23,24,25,26,27,28] research.Nonetheless, the role of trions or other e-h complexes in magneto-optical spectra is still far from being completely understood. Especially the hole gas remains relatively less thoroughly explored because of both more complicated valence band structure and a larger difficulty in achieving ultra-high carrier mobility.…”