Silicon nanowires with mean diameters of about 50-100 nm formed by wet-chemical etching of crystalline silicon wafers with low and high doping level were investigated by means of photoluminescence and Raman spectroscopy. The photoluminescence bands in the spectral ranges of 650-900 nm and near 1100 nm were detected. These emission bands are explained by the radiative recombination of excitons in small Si nanocrystals on the surface of Si nanowires and by the band gap related photoluminescence of the volume of Si nanowires, respectively. The latter band was found to be efficiently excited by the infrared laser radiation at 1064 nm. It was observed an enhancement of the photoluminescence and Raman scattering intensities in the samples of Si nanowires in comparison with crystalline Si substrates under excitation at 1064 nm. This fact can be explained by strong scattering of the excitation light, which results in partial light trapping in silicon nanowire arrays. The effects of the substrate doping level and surface orientation in the photoluminescence and Raman scattering of the structures of Si nanowires are analyzed. The observed enhanced photoluminescence and Raman scattering are discussed in view of possible application in optoelectronic and molecular sensoric.