Study of doped-intrinsic interfaces in amorphous semiconductors using doping multilayers

The constant photocurrent method (CPM) was used to study the p-i interface defect density in amorphous silicon-based p-i-p-i doping multilayers. The deep defect absorption, from CPM, of the doping multilayers was found to be between that of the bulk intrinsic ( 1016 cm-3) and doped samples ( 1018 cm-3), increasing with increasing number of periods in the multilayer structure. The Urbach tail of the multilayers is similar to that of the bulk intrinsic film. These results suggest the presence of an interfacial layer possibly associated with the width of the intrinsic layer that is contaminated by a residual tail of doping from the doped layer. From secondary-ion mass spectroscopy (SIMS) the estimated thickness of this interfacial layer is 70 angstrom. Photothermal deflection spectra (PDS) are dominated by the absorption of the doped layers and are not sensitive to the presence of intrinsic layers nor to the multilayer period.