Localized description of the electronic structure of covalent semiconductors. I. Perfect crystals

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Abstract
A localized description of covalent semiconductors is discussed as an alternative to the conventional band structure description. Localized orbitals are defined as eigenfunctions of the one-electron Hamiltonian for a finite cluster of atoms in a simulated crystalline environment. The bound electronic states of the cluster are determined by the SCF X alpha scattered wave method. It is shown that the main features of the valence band structure emerge in the spectrum of occupied cluster states. The use of the localized orbitals for the interpretation of X-ray emission spectra is justified by the localized nature of the excitations. A local density of states is defined for the interpretation of spectra of localized excitations. The information on the electronic structure, which photoelectron spectroscopy and optical absorption spectroscopy provide, is also compared to the predictions of the model. The model is particularly investigated with respect to silicon, and its general applicability to perfect crystals is tested by similar studies of diamond and germanium. The obtained results correlate very well with experimental observations.