Influence of the statistical shift of Fermi level on the conductivity behavior in microcrystalline silicon

The electrical conductivity behavior of highly crystalline undoped hydrogenated microcrystalline silicon (μc-Si:H) films having different microstructures was studied. The dark conductivity is seen to follow the Meyer Neldel rule (MNR) in some films and anti-MNR in others, depending on the details of microstructural attributes and corresponding changes in the effective density of state distributions. A band tail transport and statistical shift of the Fermi level are used to explain the origin of MNR as well as anti-MNR in our samples. We present the evidence of anti-MNR in the various experimental transport data of μc-Si:H materials reported in literature and analyze these data together with ours to show the consistency and physical plausibility of the statistical shift model. The calculated MNR parameters and other significant material parameters derived therefrom are tenable for a wide microstructural range of the μc-Si:H system.