Metastable pseudomorphic Ge0.12Si0.88films were grown by molecular beam epitaxy on Si(100) substrates and then implanted with 100 keV31P at room temperature for a dose of 5×1013/cm2. Samples were subsequently annealed by rapid thermal annealing (RTA) in nitrogen and by steady‐state furnace annealing in vacuum. Both damage and strain introduced by implantation can be completely removed, within instrumental sensitivity, by RTA at 700 °C for 10–40 s. Vacuum annealing for 30 min at 500–550 °C removes most of the damage and strain induced by the implantation but the activation of the P is poor. At 700 °C, the activation is nearly 100%, but the crystallinity worsens and the pseudomorphic strain begins to relax. We conclude that for a lightly implanted metastable and pseudomorphic GeSi epilayer on Si, steady‐state vacuum annealing cannot achieve good dopant activation without introducing significant strain relaxation to the heterostructure, while RTA can. ©1995 American Institute of Physics.