Enhancement of the binding energy of charged excitons in disordered quantum wires

Abstract

Negatively and positively charged excitons are identified in the spatially-resolved photoluminescence spectra of quantum wires. We demonstrate that charged excitons are weakly localized in disordered quantum wires. As a consequence, the enhancement of the "binding energy" of a charged exciton is caused, for a significant part, by the recoil energy transferred to the remaining charged carrier during its radiative recombination. We discover that the Coulomb correlation energy is not the sole origin of the "binding energy", in contrast to charged excitons confined in quantum dots.

Localization of excitons in disordered quantum wires probed by single-photon correlation spectroscopy

“…The energy separation between the lines of the doublet is a measure of the "binding energy" of the charged excitons. 11 Similar values of 4.2 meV for this binding energy were obtained recently for excitons in GaAs/ AlGaAs V-groove QWRs of similar dimensions. 11 Based on these findings, we assign the emission lines as coming from a negatively charged exciton ͑X − ͒-(line A) and a neutral exciton ͑X͒-(line B) localized by potential fluctuations along the lateral InGaAs/ AlGaAs QWRs.…”

“…It should be pointed out that this single photon emission was observed without the need to put small apertures in order to limit the size of the emitting wire, as is commonly done with disordered QWRs. 11 We attribute this to the gradient in the wire potential in our tapered QWRs, which disperses the emission energies along the wire axis. The photon correlation measurements also yielded spatial information concerning the recombination sites of the localized excitons, which is not available from the PL spectra.…”

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

“…The binding energies of the complexes are very small in bulk, but they are substantially enhanced in structures of reduced dimensionality, i.e., in quantum wells [2][3][4][5][6][7][8] and quantum wires. [9][10][11] Due to the larger effective mass of the hole, in bulk 12 as well as in strictly two-dimensional confinement 3 the binding energy of positive trions ͑X + ͒ is larger than the negative trion ͑X − ͒ binding energy. However, in quantum wells the observed 5 X − and X + binding energies are nearly equal, which is explained 4,5 by a stronger hole confinement within the quantum well enhancing the hole-hole interaction.…”

“…The present work is motivated by a recent experimental study 11 of positive and negative exciton trions in V-groove GaAs/ AlGaAs quantum wires. The negative trion was found to be distinctly more stable than X + ͑binding energies of X − and X + were determined as 4.2 and 2.9 meV, respectively͒.…”

Electron Raman scattering in quantum well wires

“…In this system, the band gap, the electronic structure, transport properties, third-harmonic generation, exciton and impurity levels and binding energies have been broadly investigated [1][2][3][4][5][6][7][8][9][10][11]. Besides, varieties of quantum phenomena such as lowdimensional electron states (hole states), modified dynamics of carriers in the systems and increased exciton binding energy can be provided by nanometer-scale confinements in semiconductor materials [12][13][14][15], and those quantum phenomena might be used in the field of solid-state lasers and optoelectronic devices [16].…”