Characterization of Defects in Semiconductors by Raman Spectroscopy in Low Frequency Region

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The aim of this project is to detect crystal defects or imperfections by Raman measurements of semiconductors in low frequency region. For this purpose, we have compared following two spectroscopic systems by use of a multichannel detector.(1) A combination of a filtered spectrometer and double monochromator.(2) A combination of a holographic notch filter and a double monochromator.The first system can be applied to any wavelengths of an exciting laser, but the reflection loss of the filter spectrometer was very high. Hence this system could not be convenient for the detection of weak signals in lower frequency region.It was found that the loss of signals in the second system was low and that the Raman spectra could be measured in the region down to 60 cm^<-1>. When using a Raman microscope, Raman spectra were measured down to 100 cm^<-1>.Raman spectra of SiC crystals having stacking faults were measured by the second system and analyzed.