Study of the optical properties and the density-of-states distribution of hydrogenated amorphous silicon-nitrogen alloy

Abstract

The constant-photocurrent method (CPM) and photothermal deflection spectroscopy (PDS) have been used as complementary techniques to measure the density-of-states distribution and the different optical parameters in hydrogenated amorphous silicon-nitrogen alloy (a-SiN:H). Constants such as the optical gap E _g the Urbach edge E _u or valence-band edge E _0V were obtained directly from the CPM or photothermal deflection spectra. The height of the midgap-defect density of States, its wideness or the conduction-band edge have been deduced by applying a deconvolution procedure to the measured absorption spectra. The density of surface states was also calculated. The results were based on the different sensitivities of the CPM and PDS to transitions involving unoccupied defects and surface states. We have studied the influence of nitrogen incorporation in a-SiN: H samples and the effect of hydrogen dilution.