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

We have calculated the effect of an electric field applied along the direct ion of carrier confinement on the exciton linewidth due to the scattering o f excitons by ionized impurities in semiconducting quantum well structures. The contributions to the linewidth due to the elastic and inelastic scatte ring of the excitons by the ionized impurities have both been taken into ac count. Both these contributions to the linewidth are found to increase with the applied electric field except for the narrowest wells. However, the li newidth is found to initially decrease with increasing well width for all e lectric fields and then increase again with increasing well widths for fini te 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 f ield, the linewidth continues to decrease with increasing well width. When the exciton is ionized as a result of the scattering, the linewidth increas es 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 io nized impurities. In the case of elastic scattering of the exciton by the i onized impurities, the linewidth has a maximum as a function of the exciton energy with the maximum shifting to lower energies as the well width decre ases. 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 ma ss energy with the threshold being larger for smaller well widths. The cont ribution 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. (C) 1999 American Institute of Physics. [S0021-8979(99)03820-7 ].