We performed a comparative study of the electro-physical properties of heterostructures containing PECVD nanocrystalline silicon (nc-Si) and electro-chemically etched porous silicon (PS) layers over a wide range of thicknesses, in terms of their energy parameters. Based on the proposed analytical expressions and the experimental current-voltage and capacitance-voltage characteristics, we studied the characteristics of the surface states at the nc-Si(or PS) interfaces in Pd-nc-Si(or PS)-p-Si heterostructures. The results revealed that the surface states play an essential role in the carrier transport in both types of heterostructures that were investigated. (C) 2009 Elsevier B.V. All rights reserved.