The Angle 4H-SiC Homoepitaxial Growth And A Study On Raman Scattering Spectra Of 4H-SiC Homoepitaxial Layers

Silicon carbide (SiC) belongs to the third generation of wide band gap semiconductor material. It is an important indirect bandgap semiconductor material, has excellent physical and electrical properties. Thus, SiC electronic devices are ideally suited to work in high temperature, high-frequency, high-power and many other special circumstances, in many areas they have very important value. One of the key manufacturing SiC power devices is grown homoepitaxial layer on SiC, and the doped carrier concentration is closely related to its physical and electrical properties. So we need an efficient and reliable method to investigate 4H-SiC expitaxial layer. Raman scattering is a non-invasive test method, it can be easily and quickly analyze the structure of the sample.This article uses the horizontal hot-wall CVD technique, process homoepitaxial on 4H-SiC substrate. We use three experiment to comparative the three important parameters, finally we get the most suitable carbon-silicon ratio, growth temperature and growth pressure to Raman scattering analysis. After a comparative analysis, we used the best experimental program:growth epitaxial layers with different doping levels on 8° and 2 inch n-type 4H-SiC single crystal. In preparation process SiH4 and C3H8 as the Si and C source; high purity N2 and TMA as the N and Al source doped; hydrogen as carrier gas; growth temperature is 1580℃; pressure is 100mbar.Raman spectra at room temperature for different doped concentrations’ 4H-SiC epitaxial layer. By using MATLAB fitting LOPC mode plasma frequency, and theoretically calculate carrier concentration. By comparison Raman measurement result and SIMS measurement result are in good agreement. So we can use Raman test get carrier concentration of materials.Analysis LOPC peaks we found that with the doping concentration increases, the carrier concentration increases, LOPC peaks blue shift, frequency shift becomes larger, the scattering intensity decreases, LOPC peaks width wider. LOPC peaks blue shift is related to compressive-stress. As the doping concentration increases, the Raman peaks’ FWHM be widened, which is closely related to the defects in the crystal. As the doping concentration increases, so that the free carrier concentration increases, the increases of the free carriers will make the potential reduce, and that will causing the scattering intensity decreases, consequent peak intensity changes.