Pseudomorphic Ge0.12Si0.88 films 265 nm thick grown by molecular beam epitaxy on p- Si(100) substrates were implanted with 100 keV 31P at room temperature for a dose of 5 x 1013/cm2. The projected range of the implanted P is about half the epilayer thickness. The implanted layers, together with non-implanted virgin samples, were subsequently annealed by both rapid thermal annealing in nitrogen and by steady-state furnace annealing in vacuum. The damage and strain of the annealed layers were studied by 4He channeling and x-ray doublecrystal diffraction. For a dose of 5 x 1013 P /cm2, both the damage and strain introduced by implantation can be completely removed, within instrumental sensitivity, by rapid thermal annealing at 700 °C for 10 - 40 s. Furnace annealing at 550 °C for 30 min for this sample removes most of the damage and strain induced by implantation. Furnace annealing at 700 °C or higher worsens the crystallinity of the layer and the strain relaxes. Hall measurements were performed on the same samples. Furnace annealing cannot achieve good dopant activation without introducing significant strain relaxation to the heterostructure, while rapid thermal annealing can.