Energy-level structure of two-dimensional electrons confined at theAlxGa1−xAs/GaAs interface studied by photoluminescence excitation spectroscopy

The electronic structure of one-sided modulation-doped n-channel ${\mathrm{Al}}_{\mathit{x}}$ ${\mathrm{Ga}}_{1\mathrm{-}\mathit{x}}$As/GaAs heterostructures has been studied by photoluminescence excitation spectroscopy in samples with a narrow (≊500 Å) active GaAs region. The excited two-dimensional (2D) electron states are observed optically at 2 K, and 2D hole quantization is also found to be important for the structure investigated. Theoretical calculations including exciton effects show good agreement with the experimental data.