Extended-defect aspects of state-of-the-art Ge-on-Si materials and devices are discussed with an emphasis on the impact of postgrowth thermal budget on the structural and electrical epilayer characteristics. The observations on the annealed thick and thin epitaxial layers on Si can be explained based on a thermodynamic model for the minimum density of threading dislocations (TDs). For the present processing conditions, the leakage current of Ge complementary metal oxide semiconductor compatible p(+)n junctions becomes independent of the TD density at about 10(7) cm(-2).