Spatial diffusion of excitons in n-type modulation-doped (Cd,Mn)Te/(Cd,Mg)Te single quantum wells under magnetic fields

Time-resolved and spatially resolved photoluminescence (PL) measurements were performed on the (Cd,Mn)Te-based two-dimensional (2D) electron gas system at 4.2 K under magnetic fields up to 0.5 T. The detailed characteristics of the PL spatial extent under these magnetic fields were strongly dependent upon the intrinsic 2D carrier density. We found that, in the lower carrier density sample, the PL spatial extent increased with an increase in the magnetic fields. This is contrary to the result for the nonmagnetic system. These phenomena are qualitatively interpreted by considering the competition of the mobile neutral exciton (X), localized negatively-charged exciton (X-) and, furthermore, the suppression of a free-exciton-magnetic-polaron formation, which is one of the characteristic properties of diluted magnetic semiconductors such as (Cd,Mn)Te. (C) 2003 American Institute of Physics.