Origin of multiple-peak photoluminescence spectra of light-emitting porous silicon

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Abstract
Multiple-peak structures in photoluminescence spectra of porous silicon are observed in the temperature range of 10–300 K. The peak energies are found to coincide well with the photoluminescence peak pinning energies previously reported. Thus the fine structures of luminescence spectra could be attributed to the size quantization of Si nanostructures formed during the sample preparation. After the sample was stored in atmosphere for six months, the multiple-peak structures in photoluminescence spectra still remain but the line shapes change significantly. The blueshift of the spectra is believed to be due to the variation of size distribution by natural oxidation. The size distribution for the sample showing multiple photoluminescence peaks is much more nonuniform when compared with ordinary samples and it varies from spot to spot. The measured temperature dependencies of the intensities of short-wavelength components show maxima at the temperature around 175 K, while the intensities of long-wavelength components are fairly small and dominate only at low temperatures.