Measurement of diffusion length gradients in hydrogen passivated silicon ribbon

Abstract

Hydrogen passivation of p-type Si ribbon was studied by means of diffusion length measurements using the surface photovoltage (SPV) method. The effect of gradients in diffusion length on the SPV measurements and the median depth sampled by this method were investigated by numerical solution of the appropriate diffusion equations. The SPV technique was found to give an average of the diffusion length depth distribution with a median sampling depth of 70 μm. Up to threefold increases in diffusion length were observed due to passivation. Diffusion length profiling measurements made by etching away the surface showed significant passivation occurring at a depth of 200 μm.