Molecular dynamics simulations of bulk and surface defect formation in silicon and germanium

Semiconductor devices exhibit a critical dependence on their physical structure. Therefore, epitaxial growth has become increasingly important in the fabrication of devices. One aspect of epitaxial growth, low energy (;The Molecular Dynamics (MD) technique has only recently begun to be used for semiconductors due to difficulties in modeling their highly covalent nature although it has been used successfully for metals for three decades. The development of potential energy functions such as the one developed by Tersoff has opened the door to investigations of the behavior of semiconductors in low energy regimes that cannot be performed using linearized techniques such as Monte Carlo.;MD simulations were used to investigate the formation of simple defects in the silicon bulk. The results of these simulations, when combined with a model for the bulk displacement threshold energy based on the symmetry of the crystal, yield analytical expressions for the bulk displacement threshold energy for directions near the ;For comparative purposes, several similar simulations were performed for germanium. The most interesting differences between germanium and silicon was that for comparable energies, replacement sequences occurred in germanium while they did not in silicon.;The formation of defects caused by a PKA directed into or away from the surface was thoroughly investigated for the 2 x 1 Si(001) surface. These results indicate that the perpendicular component of the energy necessary to sputter an atom is not a constant. Similar simulations were performed for the 2 x 1 Ge(001) surface. In general, the PKA energies required to affect the surface morphology and to sputter an atom were lower in germanium.