Investigation on preparation and physical properties of nanocrystalline Si/SiO2 superlattices for Si-based light-emitting devices

Structures containing silicon nanocrystals (nc-Si) are very promising for Si-based light-emitting devices. Using a technology compatible with that of silicon, a broader wavelength range of the emitted photoluminescence (PL) was obtained with nc-Si/SiO2 multilayer structures. The main characteristic of these structures is that both layers are light emitters. In this study we report results on a series of nc-Si/SiO2 multilayer periods deposited on View the MathML source thermal oxide SiO2/Si substrate. Each period contains around View the MathML source silicon thin films obtained by low-pressure chemical vapour deposition at T=625°C and View the MathML source obtained by atmospheric pressure chemical vapour deposition T=400°C. Optical and microstructural properties of the multilayer structures have been studied by spectroscopic ellipsometry (using the Bruggemann effective medium approximation model for multilayer and multicomponent films), FTIR and UV–visible reflectance spectroscopy. IR spectroscopy revealed the presence of SiOx structural entities in each nc-Si/SiO2 interface. Investigation of the PL spectra (using continuous wave-CW View the MathML source and pulsed View the MathML source laser excitation) has shown several peaks at 1.7, 2, 2.3, 2.7, 3.2 and View the MathML source, associated with the PL centres in SiO2, nc-Si and Si–SiO2 interface. Their contribution to the PL spectra depends on the number of layers in the stack.