Electrical characterisation of thin silicon layers by light beam induced current and internal quantum efficiency measurements

Thin crystalline silicon layers (50 μm) were grown by vapour phase epitaxy on monocrystalline substrates. Minority carrier diffusion length and surface recombination velocity were evaluated by light beam induced current experiment. Although it appeared difficult to apply existing analytical models to thin and high quality layers, multi-dimensional simulator DESSIS was used successfully to extract diffusion length of the order of 300 μm for p-type material and 80 μm for n-type material with surface recombination velocity of the order of 100-1000 cm s−1 when the surface was passivated by a thin silicon nitrite coating. Results were compared with the diffusion length evaluated from internal quantum efficiency analysis in fabricated photovoltaic cells made of the same material, using spectral response and reflectivity measurements.