Exciton-Exciton Interaction in Cd(S, Se) Crystals as Studied by Using Argon Ion Laser

Abstract

As to such Cd(S, Se) crystals that the position of the intrinsic A exciton coincides with the 488.0 nm argon ion laser line, photoconductivity and emission spectra were measured at 1.8°K under this laser line excitation. Photocurrent increases in proportion to the square of excitation intensity above a certain critical excitation level. This gives direct evidence for free carrier generation from high density exciton state due to exciton-exciton interaction. At higher excitation levels a new emission line due to exciton-exciton interaction appears at a position shifted by the amount of the ionization energy of the intrinsic exciton from either the intrinsic or bound exciton line, providing further evidence. The emission peaks of the intrinsic and bound excitons shift to the opposite directions with increasing excitation intensity. This is interpreted as the consequence of the screening effect mutually exerted between the two kinds of excitons.