Implantation and Activation of High Concentrations of Boron and Phosphorus in Germanium

The effect of increasing boron or phosphorus implant dose (i.e., 5×1013-5×1016 cm−2) and subsequent annealing (400-600°C for 3 hrs in N2) on the activation, diffusion and structure of germanium is studied in this work. The peak concentration of implant dose is ∼ 2×1021 cm−3. Secondary ion mass spectrometry (SIMS), spreading resistance profiling (SRP), high resolution X-ray diffraction (HRXRD), X-ray absorption fine structure (XAFS), Rutherford backscattering spectrometry (RBS), and nuclear reaction analysis (NRA) were used to characterize the implant and activation behavior. Boron is found to have a high solid solubility (i.e., > 2×1020 cm−3), even immediately after implant; while in contrast, phosphorus is limited to ∼ 1–2×1019 cm−3. Diffusion of phosphorus is also extremely extrinsic, while boron is practically immobile.