DEPTH PROFILING OF DEFECTS IN A-SIH FILMS BY MEANS OF MODULATED PHOTOCURRENT

This work reports about experimental findings obtained by means of Mod ulated Photocurrent (MPC) spectroscopy as applied to a-Si:H films in s andwich configuration. The gap density of states from 0.4 to 0.7 eV be low the conduction band edge has been recontructed for three excitatio n wavelengths. This allows for a spatial depth profiling of unoccupied defects. It is shown that the defects peak apparently shifts towards midgap when probing the region near a-Si:H-metal interface. This resul t is interpreted by means of two different models. The likelihood of t hese models is discussed by comparing the results with other spectrosc opic data.