The paper reports the sharp increase in resistivity and the conductivity change (type) in the single-crystal silicon sample doped with vanadium. The electrical and optical properties of single-crystalline silicon were determined Hall- and four-probe measurements and infrared (IR-) spectroscopy. Relative resistance, charge carrier concentration, mobility, and concentration of optically active oxygen and carbon in the samples were determined layer-by-layer. It is shown that in silicon samples doped with vanadium the concentration of optically active oxygen atoms tends to reduce.