Inverse-photoemission study of unoccupied electronic states in Ge and Si: Bulk energy bands
1986; American Physical Society; Volume: 33; Issue: 4 Linguagem: Inglês
10.1103/physrevb.33.2607
ISSN1095-3795
AutoresD. Straub, L. Ley, F. J. Himpsel,
Tópico(s)Semiconductor materials and devices
ResumoWe have measured k-resolved inverse-photoemission spectra of the Ge(111)2\ifmmode\times\else\texttimes\fi{}1 and Si(111)2\ifmmode\times\else\texttimes\fi{}1 surfaces. The main spectral features are well described in terms of direct transitions to the three lowest conduction bands along \ensuremath{\Gamma}L and a transition to a surface resonance near the conduction-band minimum via a surface umklapp process. An extra feature reflects a maximum in the density of empty states. Several critical points are determined, e.g., for Ge, ${L}_{1}$ at 0.7 eV, ${L}_{3}$ at 4.2 eV, and ${L}_{2}^{\mathcal{'}}$ at 7.9 eV and a higher L point at 11 eV, and for Si, ${L}_{1}$ at 2.4 eV and ${L}_{3}$ at 4.15 eV above the valence-band maximum. By comparing our inverse-photoemission results with those from photoemission and optical spectroscopy we find that the ${E}_{1}$ transition could be lowered by the electron-hole interaction by up to 0.15 eV for Ge and 0.5 eV for Si. A comparison with first-principles and empirical band calculations is made.
Referência(s)