Effect of an electric field on the exciton linewidth due to scattering of excitons by ionized impurities in semiconducting quantum well structures

Abstract

We have calculated the effect of an electric field applied along the direction of carrier confinement on the exciton linewidth due to the scattering of excitons by ionized impurities in semiconducting quantum well structures. The contributions to the linewidth due to the elastic and inelastic scattering of the excitons by the ionized impurities have both been taken into account. Both these contributions to the linewidth are found to increase with the applied electric field except for the narrowest wells. However, the linewidth is found to initially decrease with increasing well width for all electric fields and then increase again with increasing well widths for finite electric field for the case where the exciton is scattered elastically. The minimum in the linewidth as a function of well width shifts to smaller well widths with increasing electric field. In the absence of an electric field, the linewidth continues to decrease with increasing well width. When the exciton is ionized as a result of the scattering, the linewidth increases with well width for all nonzero electric fields. However, in the absence of the electric field, the linewidth decreases with increasing well width. This reflects the effect of decreasing confinement on the scattering by ionized impurities. In the case of elastic scattering of the exciton by the ionized impurities, the linewidth has a maximum as a function of the exciton energy with the maximum shifting to lower energies as the well width decreases. For scattering which results in the ionization of the exciton, there is a threshold in the linewidth as a function of the exciton's center of mass energy with the threshold being larger for smaller well widths. The contribution to the linewidth due to elastic scattering of the exciton is many orders of magnitude larger than that due to scattering in which the exciton is ionized. © 1999 American Institute of Physics.