Photoreflectance and photoreflectance-excitation spectroscopy of a GaAs/Ga0.67Al0.33As multiple-quantum-well structure

We have studied the pump-beam-wavelength (${\lambda }_p$) dependence of the 77-K photoreflectance (PR) of a GaAs/${\mathrm{Ga}}_{0.67}$ ${\mathrm{Al}}_{0.33}$As multiple-quantum-well structure. The PR signal as a function of ${\lambda }_p$ is a new spectroscopy denoted as photoreflectance-excitation spectroscopy (PRE). Both PR and PRE exhibit features from the $1S$ exciton states as well as continuum transitions of the fundamental heavy- and light-hole to conduction-band states, thus yielding exciton binding energies. The advantages of PRE are discussed.