Raman analysis of phonon lifetimes in 4H-SiC and their doping dependence

Abstract

We have measured the slit width dependence of the linewidth of the first-order Raman lines in 4H-SiC at room temperature. The Raman spectra were fitted into Voigt profile. The Raman linewidth monotonously increased with the slit width, which indicated that the obtained linewidth contained the contribution of instrumental bandpass. To exclude the contribution of instrumental bandpass and get the accurate data for linewidth, a mathematical method was used to eliminate the instrumental bandpass due to the finite slit width. Then the Raman linewidth at zero-slit width was employed to calculate the phonon lifetime by energy-time uncertainty relation. Results showed that for undoped 4H-SiC, the phonon lifetime was in the sequence of E2(TA) > E2(TO) > A1(LO). In addition, the impurity content effect on phonon lifetime was discussed. Results showed that phonon lifetime was shortened with increasing impurity content. However, it was found that the phonon lifetime of E2(TA) mode was more sensitive to impurity content than that of E2(TO) mode.