Advanced modeling for optical characterization of amorphous hydrogenated silicon films

Amorphous hydrogenated silicon (a-Si:H) films deposited on glass and crystalline silicon substrates are analyzed using a multi-sample method combining ellipsometry and spectrophotometry in a spectral range of 0.046–8.9 eV, utilizing an analytical dispersion model based on parametrization of joint density of states and application of sum rule. This model includes all absorption processes from phonon absorption to core electron excitations. It is shown that if films deposited on both substrates are characterized together it is possible to study both phonon absorption and weak absorption processes below the band gap, i.e. the Urbach tail and absorption on localized states.