Characterization of microvoids in thin hydrogenated amorphous silicon layers by spectroscopic ellipsometry and Fourier transform infrared spectroscopy

Microstructures of voids in a-Si:H layers on the surface of c-Si wafers were quantitatively analyzed by combining spectroscopic ellipsometry and Fourier transform infrared spectroscopy. A diameter (D) from 0.52 to 2.11 nm and a number density (Nvoids) from 8.4 × 1018 to 5.4 × 1020 cm−3 were estimated. It was demonstrated large-size voids were formed owing to the network relaxation caused by H+ etching. Measurements of the minority carrier lifetime revealed both D and Nvoids affect the passivation performance for a c-Si surface.