Electric-field and screening dependence of exciton binding energy in asymmetric double quantum well

The influence of screening by confined free electrons on the exciton binding energy in an asymmetric double quantum well is calculated for various values of applied electric field perpendicular to the layer plane. The dependence of the exciton binding energy on carrier concentration is found to be stronger for lower than for higher fields. The exciton energy drops abruptly at those field values at which the spatially direct exciton changes to the indirect one. This drop is less remarkable at higher densities of free electrons. Calculations were performed at 10 and 300 K, and up to densities of 1014 m-2 and 7 · 1014 m-2, respectively.