Interaction between excitons and 2DEG Landau levels in modulation doped GaAs/AlGaAs heterojunctions

The reflection and photoluminescence spectra of n‐type, modulation‐doped GaAs/AlxGa1−xAs wide quantum wells (QW) and heterojunctions (HJ) were studied at T = 2K and under a perpendicularly applied magnetic field. The spectra show two groups of very sharp lines that originate in two types of excitations: excitons, whose center of mass motion is quantized, and interband Landau transitions of the 2DEG, that is confined to the QW edges. Abrupt energy and intensity variations of both types of lines are observed at filling factors ν = 1,2 of the 2DEG. These variations are interpreted in terms of an interaction between excitations that are spatially confined in separate parts of the wide QW (or HJ). It leads to energy level splittings and increased exciton dissociation by the magnetized 2DEG layer.