Determination of the midgap density of states and capture cross-sections in polymorphous silicon by space-charge-limited conductivity and relaxation

A new type of material consisting of an amorphous silicon matrix, in which silicon nanoparticules are embedded, has recently been obtained. This material, named polymorphous silicon (pm-Si), exhibits enhanced transport and stability properties with respect to hydrogenated amorphous silicon (a-Si:H). In order to progress in the understanding of such improved properties, we combine space-charge-limited current and space-charge relaxation measurements which allow us to show that the density of states at the Fermi level and their capture cross sections in pm-Si are at least ten times and five times lower respectively than in a-Si:H. This is in good agreement with photoconductivity results.