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HL: Fachverband Halbleiterphysik
HL 30: Si/Ge
HL 30.9: Vortrag
Mittwoch, 25. März 2009, 11:45–12:00, POT 51
Electronic structure and effective masses in strained silicon — •Mohammed Bouhassoune1,2 and Arno Schindlmayr2 — 1Institut für Festkörperforschung, Forschungszentrum Jülich, 52425 Jülich, Germany — 2Department Physik, Universität Paderborn, 33095 Paderborn, Germany
Metal-oxide-semiconductor field-effect transistors (MOSFETs) based on strained silicon hold considerable interest for modern microelectronics, because they are compatible with existing manufacturing technology and promise higher carrier mobility and faster switching times. Here we quantitatively examine the effect of strain on the electronic structure of silicon, combining density-functional theory within the local-density approximation and the GW approximation for the electronic self-energy. Quasiparticle band structures, deformation potentials and effective masses are obtained for tetragonal, orthorhombic and trigonal distortions of the unit cell, corresponding to biaxial strain in the (100), (110) and (111) planes with full relaxation, respectively. The tetragonal and orthorhombic distortions lift the sixfold degeneracy of the conduction-band minimum. Furthermore, strain in any direction causes the band structure to warp, and an energy split between light and heavy holes occurs at the top of the valence band. The inclusion of proper self-energy corrections within the GW approximation in our work not only yields band gaps in much better agreement with experimental measurements, but also predicts slightly larger electron effective masses. Even for small strain values, these changes in the electronic structure significantly affect the mobility of the charge carriers.