Exciton to two-dimensional electron-hole photoluminescence transitions driven by the quantum Hall effect in photoexcited heterojunctions

Abstract

A comprehensive experimental study of the photoluminescence (PL) spectral evolution under a magnetic field $(B\ensuremath{\leqslant}25\phantom{\rule{0.3em}{0ex}}\mathrm{T})$ applied perpendicularly to a high-mobility two-dimensional electron gas (2DEG), is performed on modulation-doped $\mathrm{Ga}\mathrm{As}∕\mathrm{Al}\mathrm{Ga}\mathrm{As}$ heterojunctions at ${T}_{L}=0.3\phantom{\rule{0.3em}{0ex}}\mathrm{K}$. The abrupt transfer of the free exciton to hole-2DEG PL occurring at integer and fractional filling factors is analyzed in a phenomenological model, wherein free excitons photogenerated in the GaAs layer dissociate into a 2D electron and 3D hole near the 2D-electron channel. Such magnetic field induced exciton-(2De-h) transitions are able to explain the remarkable strong PL anomalies in single hetrojunctions as compared to those observed in modulation-doped quantum wells.