Comparison of the methods used to calculate the density of states from measured subbandgap absorption in a-Si:H and related alloys

Different methods used to calculate the density of states (DOS) from optical absorption spectra measured by the constant photocurrent method in a-Si:H and in the related alloys are examined. We have carried out both numerical simulations and used measured spectra to distinguish the differences between the methods. Although it depends on the shape of the measured absorption spectra, the methods using the derivative of the measured subbandgap absorption spectra give most correct DOS.