Abstract
The oscillator strength of excitons is investigated systematically in lattice-matched GaAs/As, strained-well As/GaAs, and strained-well GaAs/ quantum wells (QW’s) using Fourier-transform reflectance spectroscopy. The oscillator strength in GaAs/As QW’s increases as the well width is reduced, in agreement with the existing theory, while those in As/GaAs and GaAs/ QW’s show a maximum at a certain well width. The well-width dependence of the band nonparabolicity and the overlap of the electron and hole wave functions is responsible for this behavior. The oscillator strengths in As/GaAs and GaAs/ QW’s are differently dependent on the alloy composition; this is also explained in terms of the band nonparabolicity and the wave-function overlap. The temperature dependence of the oscillator strength in these structures is well described by a modified Debye-Waller expression with an averaged phonon mode. The exciton-phonon interaction, deduced from the temperature dependence of the oscillator strength of the zero-phonon line, is mainly determined by confined phonons in GaAs/As QW’s, and by quasi-three-dimensional phonons in As/GaAs QW’s.
- Received 11 April 1994
DOI:https://doi.org/10.1103/PhysRevB.50.7499
©1994 American Physical Society