In this work the cellular structure is proposed as a buffer layer for defect-free heteroepitaxial growth of mismatched materials. The micro-cellular buffers were formed by 80 keV In+ ion implantation into single-crystalline (001) silicon wafers (2 X 10(16) cm(-2)) followed by Q-switched laser annealing at an energy density of about 1.2-3.5 J/cm(2). The structure of the obtained surface was investigated by plan-view and cross-section transmission electron microscopy. It has been found that the In-implanted, and subsequently laser annealed, Si surface exhibits a structure consisting of a system of 'seed' pads (cells) separated by indium filled trenches (walls of the cell). The linear dimensions of the pads and trenches are measured to be 15-100 and 3-5 nm, respectively, which is close to the optimal values for defect-free epitaxial growth of mismatched materials. The obtained Si[In]/Si buffer layers were used for heteroepitaxial growth of GaAs films. The density of extended defects in GaAs grown on these buffers was found to be considerably lower as compared to conventional GaAs/Si structures grown at similar conditions.