Photoreflectance study of GaAs/AlAs superlattices: Fit to electromodulation theory

The photoreflectance (PR) spectra of several GaAs/AlAs superlattices have been measured at 300 and 77 K using monochromatic light sources (laser or monochromator) as a secondary (pump) beam, thus enabling us to study the wavelength dependence of the PR. We demonstrate for the first time that electromodulation spectra from superlattices can be fit by a third derivative functional line shape, thus making it possible to precisely determine energies, broadening parameters, amplitudes, and phases of the spectral features. This result greatly enhances the usefulness of electromodulation to study and characterize these structures. The wavelength dependence of the PR shows that there is more than one PR mechanism in superlattices, in contrast to bulk material