Visible photoluminescence has been observed in crystallized a-Si:H/a-SiNx:H multiquantum-well structures at room temperature. The MQW heterostructures consisting of 72 layers were formed by computer controlled plasma-enhanced chemical-vapor deposition method and then crystallized by Ar+ laser annealing technique. The crystallinity and average grain size of the silicon microcrystals were determined by means of Raman and x-ray diffraction spectroscopy. The crystallized samples with well-layer thickness Ls=40 Å showed an intense photoluminescence which is peaked at 2.1 eV with a full width at half-maximum of 0.25 eV. This is consistent with calculations based on the quantum confinement model.

Luminescent amorphous silicon nitride films were fabricated by plasma-enhanced chemical vapor deposition at room temperature followed by thermal oxidation at 100°C. Very bright green emissions were clearly observed with the naked eye in a bright room after the samples had been oxidized. The emission peak is located at 495nm. Fourier-transform infrared absorption spectra and results of depth profiling with x-ray photoelectron spectroscopy indicate that the introduction of oxygen is of a key role in enhancing the photoluminescence intensity of the films. Emission and excitation spectra analyses suggest that the green emission is originated from the radiative recombination in the localized states related to the Si–O bonds.

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Nanocrystalline silicon (nc-Si) was fabricated by KrF excimer laser annealing of hydrogenated amorphous silicon/amorphous-SiNx:H superlattices. A stable and reproducible electroluminescence (EL) based on these structures was observed at room temperature. It was found that the EL peak was significantly blueshifted from 780 to 600 nm with decreasing the a-Si:H sublayer thickness from 4.0 to 1.0 nm, while the intensity was also notably enhanced. The results suggest that the quantum confinement effect may play an essential role in visible light emissions from our present samples.

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