纳米SiC薄膜的光电特性

AbstractAbstractHexagonal nano-silicon carbide (nano-SiC)thin films doped and undoped withphosphorus which possess a characteristic of the ultraviolet photoluminescence (PL)havebeen deposited by helicon wave plasma enhanced chemical vapour deposition techniqueunder the high hydrogen condition in this work.The optical and electric properties of thedoped nano-Sic films together with the electric and photovoltage properties of the n-pnc-SiC/Si heterojunction is studied and analyzed.The structure characteristics of n-type nano-SiC and the doping mechanism isinvestigated by Fourier transform infrared spectroscopy,Raman scattering,transmissionelectron microscope,atomic force microscopy and X-ray Diffraction.The results show thatthe crystalline volume fraction of these films is increased with doping proportion and thedoping mechanism is Si or C substituted by phosphorus.The optical absorption and PLanalysis show that with increasing the doping proportion,the band tail absorption and the PLintensity is enhanced.The conductivity analysis shows that the greatest conductivity is 10-2S.cm-1 obtained at the 1%doping proportion.It has been evidenced that there are twodifferent conduction mechanisms in the n-type nano-SiC films:one is the extended statesconduction which is dominated at a higher temperature;the other is the hopping conductionthrough the localized states near the Fermi level under a lower temperature.The I-V characterof n-p nc-SiC/Si heterojunction diode is also investigated,we obtain that the best rectificationratio is about 350 and the ideality factor is 1.89,which suggest that the forward current at lowvoltage is a generation-recombination processes likely due to defects at the nc-SiC/Siinterface.This forward current comes from the emission and diffuse process under highvoltage but the reverse current is from a Muti-step tunneling process through the interfacestates.The research on the photovoltage character of this nc-SiC/Si heterojunction indicates thatSic can serve for the window layer for Silicon based photoelectric apparatus.Thephotovoltage is mainly from the interface space charge region (SCR)and it is greatlyⅡ