The paper presents the results of study of the electrophysical properties of metal–semiconductor junctions, where the influence of the structural-impurity state of the semiconductor substrate and deposited film is significant. The influence of different preparing modes for the silicon substrate, including the thermal gettering treatment, on minority charge-carrier lifetime and on the concentration of electrically active impurity defects in the surface layer of $n$-Si is considered. The calculation results of the $I$–$V$ characteristics of Fe/$n$-Si and (Fe + C)/$n$-Si junctions are presented with the proposed method for the quantification of their rectifying capabilities. The influence of the Fe film surface oxide and its alloying with carbon on the rectifying capability of the Fe/$n$-Si junctions is shown. The decreasing of the rectifying capability of the (Fe + C)/$n$-Si junction is established using the unique method for measuring the electrophysical properties of thin-film junction under conditions of an increase in external mechanical load.