Photoelectron Spectroscopy.

We have briefly discussed a wide range of spectroscopic techniques that involve the use of electrons and/or photons. These techniques yield very detailed information about occupied and empty electron energy bands and also core levels of semiconductors. The angle-resolved versions of photoemission and inverse photoemission have produced convincing pictures of the E(k) dependence of bulk electronic states. They also have yielded information on surface states. We presented spectra of excitations of core levels and discussed the information that can be obtained from them. We also introduced the concepts of surface reconstruction, electronic surface states, and surface energy bands, and presented a few phenomena related to them, such as Fermi level pinning. This led to a brief discussion of the technologically important concepts of charge depletion and enrichment layers at semiconductor surfaces. [ABSTRACT FROM AUTHOR]