Photo-generated Carriers Decay Properties Of Nano-SiC Films

Nanocrystalline silicon carbide (nc-SiC) thin films are deposited by the helicon wave plasma-enhanced chemical vapour deposition technique. A variety of techniques, such as Fourier transform infrared spectroscopy, ultraviolet–visible transmittance spectroscopy, and atomic force microscopy are used to characteristerize the microstructure of nc-SiC thin films. The photoluminescence (PL) and photo-generated carriers decay properties of nano-SiC films have been studied.The main bands of the PL spectrum of nc-SiC films become blueshift with increasing rf bias. This result is ascribed to the enhancement of quantum confinement effect arosed by the decrease of nc-SiC grain sizes. The fixed PL peak which added to the main band is concerned compactly with surface defect of nc-SiC. The intensity of oxygen defect luminescence decrease with the augment of rf bias.The result show that rf bias can restrain the oxygen defect formation .The photo-generated carrier decay behavior of nanocrystallineβ-SiC films is measured by microwave absorption technique. The results show that the transient decay behavior of the films is closely related with their micro-structrue. The nonradiative recombination which gives priority to the photo-generated carriers decay process involves multiple energy transition processes. A relationship between the time constant and the energy location has been obtained. The fast photo-generated carrier decay process in all the samples at different rf bias is relate to the radiative recombination, while the slow carrier decay is mainly determined by the traps of two type of defect. Thecontribution of fast carrier decay process and the trap depth are both increase with the increasing rf bias. Based on the above work and the analysis of the sample structure properties,a basic model ofβ-SiC photo-generated carriers decay is proposed and the dynamic process of carrier decay in nano-SiC films is discussed.