Ion-implantation characteristics and dopant activation behavior of P in Ge have been investigated. A Monte Carlo simulation indicates a smaller projected range and consequently a smaller critical dose of amorphization for Ge compared to Si. The solid-phase epitaxial (SPE) regrowth characteristics of damaged layers for Ge clearly depend on crystal orientation of the substrate in completely amorphized samples, while no orientation dependent regrowth is observed in the partially amorphized samples. These phenomena were explained on the basis of the damage cluster model. In addition, maximum carrier activation coincides with the complete regrowth at annealing temperatures of 300-400 degrees C in completely amorphized samples. However, higher temperature annealing (500-550 degrees C) is necessary for maximum carrier activation in partially amorphized samples, although SPE regrowth completes around 250-300 degrees C. Analysis of the temperature dependence of carrier activation ratio in partially amorphized samples suggests that carrier-activation should be mediated by vacancy-migration. (C) 2011 Elsevier B. V. All rights reserved.