Quantized polarization waves of excitons at semiconductor surfaces.

Charged semiconductor surfaces may have deep and wide potential wells which can entrap Mott-Wannier excitons. For a model Morse potential (cut off at the surface), we have solved analytically the coupled wave equation and equation of motion with allowance for spatial dispersion. Coupling to TM-polarized light leads to quantized resonances corresponding to both transverse and polarization waves. These are manifest in the reflectivity spectrum as strong maxima and minima, respectively. The spectra are extremely sensitive to surface structure and thus may serve as a diagnostic tool.