Hydrogen transport in doped and undoped polycrystalline silicon

Hydrogen diffusion in B, P, and undoped poly-Si is investigated. The diffusion activation energy, EA, depends significantly on the Fermi energy, EF, and the H concentration. EA varies between 0.1 eV and 1.69 eV, accompanied by a variation of the diffusion prefactor D0 by 12 orders of magnitude. Using the theoretical value of D0, the energy E¯A required to yield the measured diffusion coefficients was calculated. E¯A depends strongly on EF and agrees well with the theoretical EF dependence of the formation energies of H+ or H−. To account for this behavior a modified H transport model based on trap-limited diffusion is proposed.