High-quality Ge epilayers on Si with low threading-dislocation densities

High-quality Ge epilayers on Si with low threading-dislocation densities we re achieved by a two-step ultrahigh vacuum/chemical-vapor-deposition proces s followed by cyclic thermal annealing. On large Si wafers, Ge on Si with t hreading-dislocation density of 2.3 x 10(7) cm(-2) was obtained. Combining selective area growth with cyclic thermal annealing produced an average thr eading-dislocation density of 2.3 x 10(6) cm(-2).We also demonstrated small mesas of Ge on Si with no threading dislocations. The process described in this letter for making high-quality Ge on Si is uncomplicated and can be e asily integrated with standard Si processes. (C) 1999 American Institute of Physics. [S0003-6951(99)03745-6].