Study of Si-Ge interdiffusion with phosphorus doping

摘要

Si-Ge interdiffusion with phosphorus doping was investigated by both experiments and modeling. Ge/Si_(1-x)Ge_x/Ge multi-layer structures with 0.75 < x_(Ge) < 1, a mid-10~(18) to low-10~(19) cm~(-3) P doping, and a dislocation density of 10~8 to 10~9 cm~(-2) range were studied. The P-doped sample shows an accelerated Si-Ge interdiffusivity, which is 2-8 times of that of the undoped sample. The doping dependence of the Si-Ge interdiffusion was modelled by a Fermi-enhancement factor. The results show that the Si-Ge interdiffusion coefficient is proportional to n~2_i~2 for the conditions studied, which indicates that the interdiffusion in a high Ge fraction range with n-type doping is dominated by V~(2-) defects. The Fermi-enhancement factor was shown to have a relatively weak dependence on the temperature and the Ge fraction. The results are relevant to the structure and thermal processing condition design of n-type doped Ge/Si and Ge/SiGe based devices such as Ge/Si lasers.