Complete valence-band structure of Ge determined by photoemission.

Abstract

The valence-band structure along the high-symmetry directions \ensuremath{\Gamma}L, \ensuremath{\Gamma}X, and \ensuremath{\Gamma}KX was studied with synchrotron radiation for a wide photon energy range (10--106 eV). A cylindrically shaped Ge crystal with [11\ifmmode\bar\else\textasciimacron\fi{}0] axis was used, which allowed us to record the spectra in normal emission for different orientations. The data were analyzed by applying the model of direct transition into free-electron final-state bands. Due to the wide photon energy range, a complete band scheme along the three directions including critical points was obtained. The data are compared with theoretical results and other measurements. The bands along the \ensuremath{\Gamma}KX direction are reported for the first time to our knowledge. Applying the wide photon energy range, the inner potential ${\mathit{V}}_{0}$=-8.8 eV was determined self-consistently using the method suggested by Middelmann et al. [Phys. Rev. B 34, 957 (1986)].