Raman scattering properties of structural defects in SiC

Abstract

Although silicon carbide crystals have been commercially available, the structural discontinuity in crystal always leads to complex interplay between the atomic positions and the electronic structures, hence results in the crystal reconstructing structurally and electronically. Here we investigate the vibrational properties of 6H-SiC (6H-polytype silicon carbide) crystals containing structural defects, e.g. micropipes (MPs), screw-dislocations (SDs) and threading dislocations (TDs), by Raman scattering. For the first-order Raman scattering, the intensity of the transverse optical phonon band centered at ~796 cm-1 , which corresponds to the phonon mode at the Γ point in 3C-SiC (3C-polytype silicon carbide), is sensitive to these structural defects. But the second-order Raman features of the structural defects have no distinguished difference. In addition, the carrier concentration within an MP might be higher than that in a SD or a TD, revealing that the carrier traps surrounding the MP are lower than that for the SD or TD. These results offer a simple way for investigating the electrical properties of structural defects in SiC crystals.

Migration behaviour of selenium implanted into polycrystalline 3C–SiC

“…11 (a) also shows that the FWHM of LO mode obtained from the sample annealed at 1000 °C (12.4 cm -1 ) is broader in comparison with the virgin sample (9.6 cm -1 ). The broadness of the Raman band indicates the presence of defects and a poor crystallinity [22]. With increased annealing temperature, the FWHM decreased gradually and became 10.6 cm -1 , which is broader than the one observed in the virgin indicating that defects are still present.…”

Defect Inspection Techniques in SiC

“…Feng et al find the peak center shift and the intensity variation of micropipes, TSDs and TEDs, as shown in Fig. 4e [48]. For spatial information, an image of Raman mapping is shown in Fig.…”

“…d A real-color CL SEM image of SF at room temperature [47]. e Raman spectrum of various defects [48]. f Micro-Raman intensity map of the 204 cm −1 peak of a micropipe-related defect [49] of nanometers.…”

Effects of swift heavy ion irradiation and annealing on the microstructure and recrystallizationof SiC pre-implanted with Sr ions

“…After annealing the as-implanted and SHIs irradiated samples at 1,200 °C, the Raman spectra showed increased narrowing of the TO and LO modes of SiC indicating more recovery (i.e., recrystallization) of the SiC structure (Feng and Zang, 2016), due to annealing at 1,200 °C as seen in Figure 10. At 1,200 °C, as-implanted samples had higher LO mode intensity (see Figure 10) and a larger average crystals size (see Table 1)…”

“…The variations in Raman peakpositions and intensities were accompanied by an increase in the full width at half maximum (FWHM) of the SiC Raman prominent peak (i.e., LO mode) from 9.4 cm −1 (virgin) to 11.6 cm −1 for the as-implanted samples, 11.8 cm −1 and 19.6 cm −1 for irradiated samples to fluences of 3.4 × 10 14 cm −2 and 8.4 × 10 14 cm −2 respectively (see Figure 7). Figure 7 shows the FWHM, intensity and peak position of LO mode in the virgin SiC, as-implanted and SHIs irradiated samples after sequentially annealing from 1,100 °C to 1,400 °C.Feng et al (Feng and Zang, 2016) found that the structural defects in SiC reduced the phonon lifetime, and hence caused a broadening of phonon Raman bands. Thus, the increase in the FWHM indicates the existence of some kind of disordering.…”