Intersubband collective excitations at the surface of a semiconductor superlattice

The intersubband and intrasubband collective excitations of a semi-infinite semiconductor superlattice are investigated. Surface intersubband excitations, similar to the intrasubband surface modes predicted by Giuliani and Quinn, are found for wavelengths shorter than a critical value ${\lambda }^{\mathrm{*}}$, which depends on the material parameters.