A THEORETICAL-MODEL FOR THREADING DISLOCATION REDUCTION DURING SELECTIVE-AREA GROWTH

An analytic model, developed earlier for understanding the reduction k inetics of threading dislocations (TDs) in the heteroepitaxial growth of thin films, is considered here for the special case of selective ar ea growth, wherein mesas of comparatively small lateral dimension are grown on a substrate. TD ensembles are treated in close analogy with c hemical species in chemical reaction kinetics. In addition, a computer simulation approach that incorporates specific TD crystallography and considers the individual geometry of and reactions between TDs is use d to augment the analytic results. The model is applied to three mesa geometries, encompassing squares as well as a rectangle. It is found t hat the density of TDs decays exponentially with increasing film growt h, consistent with the enhanced reduction noted in several experimenta l reports. (C) 1997 Elsevier Science S.A.