Very low densities of localized states at the Fermi level in hydrogenated polymorphous silicon from capacitance and space-charge-limited current measurements

The density of states at the Fermi level N(E_F) has been measured on hydrogenated polymorphous (pm-Si:H) silicon samples using both capacitance measurements on Schottky barriers and space-charge-limited current measurements on n⁺/i/n⁺ structures. From both techniques, N(E_F) values of 7-8×10¹⁴cm^-3eV^-1 have been obtained, which is significantly lower than reported in the literature for hydrogenated amorphous silicon (a-Si:H). Such values demonstrate that pm-Si:H is a very low defect density material which should be able to replace a-Si:H in the field of applications like photovoltaics.