Abstract

Magnetooptical studies of a quasi-2-D electron or hole gas in semiconductor heterostructures have been widely applied to obtain information about details of Landau quantization, screening, many-body interactions, and so on. Yet there are few experimental results which show an explicit connection between optical probe and transport measurements in quantizing magnetic fields. Here we present experimental results for a 2-D electron system in an (In, Ga)As quantum well structure, which strongly suggests a direct link between specific features in photoluminescence (PL) spectra and the longitudinal Hall resistance in the QHE regime. We demonstrate an optical effect where an excitonlike interband transition can be used as a sensitive probe of the equilibrium 2-D electron gas. This transition originates from a normally unoccupied n = 2 conduction subband level, which lies very near the Fermi level E_F of the 2-D gas in the n = 1 subband. In the zero magnetic field, the transition is similar to the recently studied many-body Fermi-edge singularity in the interband spectra of doped (In,Ga)As and GaAs quantum wells.^1,2 In finite fields the Coulomb coupling of this exciton to the 2-D electron gas in our case is strongly field dependent, a feature which appears to be directly correlated with 2-D electron occupancy within the localized or delocalized states of a Landau level.

© 1990 Optical Society of America