Si-implanted, unstrained Si1-xGex layers of various Ge concentrations ranging from 0% to 50% were grown by molecular beam epitaxy on top of a Si substrate. The samples were subjected to a 750 degreesC anneal for 180 min to explore the subsequent defect structure. Plan-view transmission electron microscopy was implemented to investigate the evolution of defects. The Si1-xGex samples with less than or equal to5% Ge exhibit {311} defect formation and dissolution, and these defects ripen throughout the course of the anneal. Increasing the Ge content has an adverse effect on the growth of {311} defects. The samples with Ge contents greater than or equal to25% demonstrated only dislocation loop formation. Dislocation loop formation and the observed impedance of {311} defect growth is facilitated by increasing the Ge content due to the weak bonding associated with the Ge atoms. (C) 2004 American Vacuum Society.