Excitons diffusion in (Cd,Mn)Te-based two-dimensional electron system under magnetic fields

Spatial diffusion of excitons in n-type modulation-doped (Cd,Mn)Te/(Cd,Mg)Te single quantum wells (SQWs) was studied through time- and spatially resolved photoluminescence (PL) measurements at View the MathML source under magnetic fields up to View the MathML source. The PL spatial extent exceeded the laser spot in all samples studied here, however, the detailed manners were strongly dependent upon the intrinsic 2D carrier density. We found the PL spatial extent got larger with the increase of magnetic fields in the case of the lower carrier density sample. It is the opposite result to the case of non-magnetic SQW. These phenomena are qualitatively interpreted by considering the competition of 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 semiconductor such as (Cd,Mn)Te.