Demonstration of excitation-dependent grain-boundary recombination velocity in polycrystalline silicon

Abstract

The dependence of grain-boundary recombination velocity on the excitation (excess carrier density) at the grain boundary is experimentally demonstrated using electron-beam-induced-current (EBIC) measurements. To facilitate quantitative interpretation of the EBIC measurements, the underlying carrier transport problem in the adjacent grains, subject to the nonlinear boundary condition at the grain boundary, is solved using computer-aided numerical analysis. By comparing the theoretical and experimental EBIC responses, values for the surface-state density at unpassivated and passivated grain boundaries and for the diffusion length in the grains in Wacker (cast) polycrystalline silicon are derived.