Photoluminescence of a high mobility 2DEG in the fractional quantum hall effect regime

The magneto-PL spectra of modulation-doped, ultra-high mobility GaAs/AlGaAs single heterojunctions (HJs) were studied under a perpendicularly applied magnetic field up to 33 T and at temperatures of 0.3 and 1.2 K. The spectra show remarkable intensity redistribution between free (bulk) exciton and 2DEG-hole PL channels occurring at electron rilling factors, v = 2 and 1. At 0.3 K, significant 2DEG-hole PL spectral changes are observed near v =2/3 and 1/3. Several heterojunctions with 2DEG density in the range of n_2D = (1 - 2.7) · 10¹¹ cm^-2 display similar features. These spectral peculiarities are attributed to the modification of the 2DEG energy spectrum caused by the e-e interaction, in particular, the recombination of valence hole with the composite (fractionally-charged) particles of the magnetized 2DEG. In HJs with lower n_2D < 10¹¹ cm ^-2, the observed PL evolution at v < 1 is mainly determined by an intensity redistribution between the σ⁺ and σ^- circularly-polarized free exciton PL components. In this case, the exciton energy is lower than the energy of the 2DEG-hole system, so that the free excitons do not dissociate near the magnetized 2DEG and thus, the 2DEG-hole PL is barely observed.