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 i n a-Si:H have been obtained by applying a new self-consisting deconvol ution procedure to the absorption spectra. This deconvolution does not suffer from the limitations of other methods because no simplifying a ssumption are made on the shape of the localized states below the Ferm i level. Numerical simulations confirm the reliability of our procedur e. The results show that the main corrections with respect to the resu lts obtained by means of the derivative method are related to the dist ribution of the deep defects. The difference between the results as ob tained by constant photocurrent method and photothermal deflection spe ctroscopy is explained in terms of different sensitivities of the two techniques to transitions involving unoccupied defects and surface sta tes.