Dopant activation and epitaxial regrowth in P-implanted pseudomorphic Ge_0.12Si_0.88 layers on Si(100)

A pseudomorphic Ge_0.12Si_0.88 film 265 nm thick grown on a Si(100) substrate by molecular beam epitaxy was implanted at room temperature with a dose of 1.5 × 10¹⁵ cm² of 100 keV P ions. The projected range of the ions is about 125 nm, which is well within the film thickness. Only the top portion of the Ge_0.12Si_0.88 layer was amorphized by the implantation. Both implanted and non-implanted samples were subsequently annealed in vacuum for 30 minutes from 400 °C to 800 °C. Values of electron Hall sheet mobility and concentration in the implanted Ge_0.12Si_0.88 epilayer were measured after annealing. The solid phase epitaxial regrowth is complete at 550 °C, where the implanted phosphorus reaches approx. 100% activation. The regrown Ge_0.12Si_0.88 layer exhibits inferior crystalline quality to that of the virgin sample and is relaxed, but the non-implanted portion of the film remains pseudomorphic at 550 °C. When annealed at 800 °C, the strain in the whole epilayer relaxes. The sheet electron mobility values measured at room temperature in the regrown samples (T_ann ≥ 550 °C) are about 20% less than those of pure Si.