SURFACE AND BULK-DENSITY OF STATES ANALYSIS IN A-SI-H BY A NEW INTERPRETATION OF PDS AND CPM MEASUREMENTS

A new experimental confirmation of the unsensitivity of photoconductive techniques to surface states in amorphous silicon thin films is provided. On the other hand, it is shown how photothermal methods, which are sensitive to the surface/interface absorption, can be useful to separate, in some cases, its contribution from the bulk one. Results on device-quality amorphous silicon films are presented and discussed together with other effects, regarding the substrate contribution, the film dishomogeneity and the spectral dependence of the photocarrier lifetime.