ACCURATE RECONSTRUCTION OF THE DENSITY-OF-STATES IN A-SI-H BY CONSTANT PHOTOCURRENT METHOD AND PHOTOTHERMAL DEFLECTION SPECTROSCOPY

Detailed results about the distribution of occupied localized states in a-Si:H have been obtained by applying a new self-consisting deconvolution procedure to the absorption spectra. This deconvolution does not suffer from the limitations of other methods because no simplifying assumption are made on the shape of the localized states below the Fermi level. Numerical simulations confirm the reliability of our procedure. The results show that the main corrections with respect to the results obtained by means of the derivative method are related to the distribution of the deep defects. The difference between the results as obtained by constant photocurrent method and photothermal deflection spectroscopy is explained in terms of different sensitivities of the two techniques to transitions involving unoccupied defects and surface states.