Magneto-optical investigations of a GaAs/AlGaAs Single Heterojunction

Magneto-photoluminescence (MPL) of a modulation-doped GaAs/AlGaAs single heterojunction has been studied in fields to 50T using a short-pulse magnet in the temperature range of 0.4K to 4K. Simultaneous transport data taken under laser illumination showed that the sample had an electron density of about 2 × 10^11cm^-2 in the first subband (E0); the second subband (E1) was empty. At T=4K, from 0- 5T the MPL data displayed both E1-HH and E0-HH magneto-exciton transitions. At 0.5K, the spectrum was dominated by a single E1-HH magneto-exciton transition. Above 4T, this magneto-exciton peak rapidly lost intensity and a new peak from the lowest 0-0 band-to-band Landau level transition appeared at a lower energy. Circular polarization analysis showed that this was a spin-up transition. At 8 T, close to filling factor ν =1, this spin-up transition disappeared and was replaced with a red-shifted L-L excitation with spin-down polarization. Its intensity rapidly increased and showed marked oscillatory behavour at various fractional quantum Hall states. To account for this behaviour, Skyrmion-hole recombination is considered. * This work is supported by NSF, State of Florida and the US DoE.