High phosphorous doped germanium: Dopant diffusion and modeling

摘要

The in situ n-type doping of Ge thin films epitaxial grown on Si substrates is limited to 1 × 10~(19)cm~(-3) by the phosphorous out-diffusion during growth at 600 ℃. By studying the phosphorous diffusion in Ge with different background doping, we find that the diffusion coefficient is extrinsic and is enhanced 100 times in Ge doped at 1 ×10~(19)cm~(-3) compared to intrinsic diffusivity. To achieve higher phosphorous concentration, delta-doped layers are used as a dopant source for phosphorous in-diffusion. We show that the doping level is a result of the competition between in-diffusion and dopant loss. The high diffusivity at high n-type carrier concentration leads to a uniform distribution of phosphorous in Ge with the concentration above 3 ×10~(19) cm~(-3).