Atomistic Modeling of Misfit Dislocations for Ge/(001)Si and Ge/(111)Si

Abstract

For Ge films on (001)- and (111)-Si the energy of coherent and semicoherent interfaces with misfit dislocations is numerically analyzed by use of the atomistic, anharmonic bond charge model. The model describes correctly the elastic properties of the Ge film and the Si substrate, the bond angle stiffness reduction for short wavelength deformations as found in the dislocation cores, and the third order elastic constants. A generalization of the model to deal with mixed Ge–Si bonds is provided. For Ge/(001)Si misfit dislocations of 90° Lomer type are considered, for Ge/(111)Si a trigonal network of 90° glide-set partials with stacking faults between them. In both cases, the estimated critical thickness for the coherent interface is in fair accordance with experimental observations.