Determination of grain-boundary parameters of polycrystalline silicon by ac electron-beam-induced current

A method for determining local parameters in polycrystalline silicon with ‘‘columnar’’ boundaries is described. The effective recombination velocity at the boundary, the diffusion length, and the lifetime of the minority carriers are determined by measuring the first Fourier harmonic of the short-circuit current generated at a shallow n+p junction by a gated electron beam. In the theoretical analysis diffusion length, lifetime, and effective recombination velocity of the carriers as well as lumped parameters of the junction are taken into account. A simple relation is found for determining the lifetime. The experimental measurement is made on polycrystalline silicon solar cells using an electron probe microanalyzer.