Photoluminescence and Raman Scattering in Arrays of Silicon Nanowires

Arrays of silicon (Si) nanowires with mean diameters of about 50-100 nm formed by wet-chemical etching of crystalline silicon wafers with low and high doping levels were investigated by means of photoluminescence and Raman spectroscopy. The photoluminescence bands in the spectral ranges of 650-900 nm and about 1100 nm were detected and explained by the radiative recombination of excitons confined in Si nanocrystals on the surface of Si nanowires and by the interband photoluminescence in the volume of Si nanowires, respectively. The intensities of the band-gap related photoluminescence and Raman scattering under excitation at 1064 nm were significantly larger for the Si nanowire samples in comparison with that for the crystalline Si substrates. This fact is explained by strong scattering of the excitation light, which results in partial light trapping in silicon nanowire arrays. The doping level and surface orientation of the substrate were found to influence the photoluminescence and Raman scattering in Si nanowire arrays.