High phosphorous doped germanium: Dopant diffusion and modeling

Abstract

The in situ n-type doping of Ge thin films epitaxial grown on Si substrates is limited to 1 × 1019 cm−3 by the phosphorous out-diffusion during growth at 600 °C. 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 × 1019 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 × 1019 cm−3.

Diffusion ofn-type dopants in germanium

“…Further experiments reported in the literature on donor diffusion in ion-implanted Ge also consistently support the strong doping dependence of diffusion. 41,[80][81][82][83][84] These studies confirm the dependence of donor diffusion on the square of the free carrier concentration. However, implantation damage gives rise to enhanced donor diffusion, in particular, at short diffusion times.…”

Excess carrier lifetimes in Ge layers on Si

“…Therefore, we ascribe the rapid decay of sample nGe to the aggregation of dopant atoms during the annealing, as the solubility limit of phosphorus might be exceeded, especially in the region close to the surface. 22 The selectively grown Ge (sample selGe, green squares in Fig. 3) does not suffer from this deterioration of the decay time, although it went through similar annealing cycles.…”

In situ doped phosphorus diffusion behavior in germanium epilayer on silicon substrate by ultra-high vacuum chemical vapor deposition

“…[15][16][17] However, a few experiments on the in situ phosphorus diffusion into the intrinsic epitaxial Ge on Si during the growth process by ultra high vacuum chemical vapor (UHV/CVD) system or reduced pressure-chemical vapor deposition (RP-CVD) were reported. [18][19][20] Well understanding in situ phosphorus diffusion behaviors during the growth of Ge on Si is necessary for Si-based Ge device applications.…”