Theory of neutral and charged exciton scattering with electrons in semiconductor quantum wells

TL;DR

This paper develops a microscopic theoretical model to analyze how electrons scatter off neutral and charged excitons in semiconductor quantum wells, revealing differences in linewidths and spectral features.

Contribution

It introduces a detailed microscopic model for exciton-electron scattering, including elastic and dissociating processes, and calculates the resulting spectral effects in quantum wells.

Findings

Charged excitons have roughly twice the linewidth of neutral excitons at given conditions.

The model predicts reflection spectra considering neutral and charged excitons with specific oscillator strengths.

The interaction matrix elements differ significantly between neutral and charged excitons, affecting their scattering behavior.

Abstract

Electron scattering on both neutral ($X$) and charged ($X^-$) excitons in quantum wells is studied theoretically. A microscopic model is presented, taking into account both elastic and dissociating scattering. The model is based on calculating the exciton-electron direct and exchange interaction matrix elements, from which we derive the exciton scattering rates. We find that for an electron density of $10^9 {\rm cm}^{-2}$ in a GaAs QW at $T=5K$, the $X^-$ linewidth due to electron scattering is roughly twice as large as that of the neutral exciton. This reflects both the $X^-$ larger interaction matrix elements compared with those of $X$, and their different dependence on the transferred momentum. Calculated reflection spectra can then be obtained by considering the three electronic excitations of the system, namely, the heavy-hole and light-hole 1S neutral excitons, and the heavy-hole 1S charged exciton, with the appropriate oscillator strengths.