First-Principles Electronic Structure Theory for Semi-infinite Semiconductors with Applications to Ge(001) (2×1) and Si(001) (2×1)

Abstract

The electronic structure of semi-ir\flnite semiconductors with energy-optimized reconstructed surfaces is calculated self-consistently for the first time. Using local-density-functional formalism and scattering theory, the calculations yield the potential, charge density, surface band structure, and wave-vector-resolved layer densities of states with extreme spectral resolution. The results quantitatively explain recent surface spectroscopy data on occupied and empty states for Ge(001)(2x 1) andSi(001)(2xl).

Surface states on clean Ge(001)2×1 surfaces

“…Firstprinciples electronic structure calculations by Kruger et al [3] [14,18,25] showed features at -0.5 eV (-0.6 eV), -1.3 eV [14,18] and -2.4 eV [25]. Our ellipsometric measurements are essentially consistent with STM measurements [2,11], angle-resolved photoelectron spectroscopy measurements [14,18,25] and theoretical calculations [3].…”

Optical anisotropy of Ge(001)2 × 1

“…The surface states are attributed to filled (empty) dimer states Di(D*), filled (empty) dangling bonds Dup (Ddown) and the back-bonds B 1 and B E. Predominant symmetries have been derived for these six states from refs. [7][8][9][10] and are listed in table 1. In table 2 the transition energies estimated from these references for transitions between the four filled and two empty states are given.…”

“…The electronic structure around the Fermi level of the clean Ge(001)2 × 1 surface is known from a number of theoretical and experimental investigations [7][8][9][10]. The surface states are attributed to filled (empty) dimer states Di(D*), filled (empty) dangling bonds Dup (Ddown) and the back-bonds B 1 and B E. Predominant symmetries have been derived for these six states from refs.…”

“…1 and it is the building stone for the 2 × 1 reconstruction observed at room temperature. The electronic structure of the thus reconstructed surface has been found, theoretically and experimentally, to be different in the directions parallel and perpendicular to the dimer bond [7][8][9][10]. Hence the optical reflection in these two directions will also be different, while the bulk of the material is optically isotropic.…”

“…This surface can lower its energy by the formation of a dimer bond between the two first-layer atoms [6][7][8][9][10]. There is still a discussion about whether the dimer is symmetric or not, in this work asymmetric dimers are assumed.…”