Multiscale modeling of point defects in strained silicon

A multiscale Green´s function method is described for modeling impurities in strained silicon. The model seamlessly links the length scales from atomistic to macro. The model accounts for the discrete lattice effects, elastic anisotropy, nonlinear effects, and the presence of point defects as well as surfaces and interfaces in the solid. An effective force, called the Kanzaki force, is defined, which is a characteristic of the defect configuration. This force can be calculated and stored for later use, which makes the method numerically convenient for subsequent calculations. The Kanzaki force is used to calculate the dipole tensor that is a measure of the strength of the defects and can be directly used to calculate the strains from the familiar continuum Green´s function. Numerical results are presented for the lattice distortion and the dipole tensors for various point defects (vacancy and substitutional germanium and carbon impurities) in strained silicon. Calculated values of elastic constants are reported for strained silicon.