HYDROGEN MIGRATION IN POLY-Si; AN ACTIVE MATERIAL FOR PHOTOVOLTAIC DEVICES AND LARGE AREA APPLICATIONS

摘要

Hydrogen diffusion in phosphorous and boron doped polycrystalline and microcrystalline silicon was investigated by deuterium diffusion experiments. The presence of dopants enhances hydrogen diffusion. The effective diffusion coefficient D_(eff) is thermally activated and the activation energy varies between 0.1 and 0.4 eV in doped poly-Si. This is accompanied by a variation of the diffusion prefactor by more than 15 orders of magnitude. Using the theoretical diffusion prefactor the energy required to yield D_(eff) was calculated. E_A also depends strongly on the Fermi energy and exhibits a similar dependence as the formation energies of H~+ and H~- in single crystal silicon. Based on the experimental data a modified trap dominated diffusion model is proposed.