Anharmonic effect on first-order Raman modes of p-type 6H-SiC single crystals

Abstract

Raman spectra of p-type 6H-SiC single crystals with different aluminum concentrations were investigated from 203 to 653 K. The temperature dependence of phonon modes were analyzed by considering the contributions from the thermal expansion and anharmonic effect. Results showed that the E2(low) and E2(high) modes were less dependent on the aluminum contents, while A1(LO) mode exhibited a strong dependence of aluminum contents. And The different feature of A1(LO) from E2(low) and E2(high) modes in heavily aluminum doped 6H-SiC indicated that the A1(LO) mode was dominated not only by the thermal expansion and anharmonic effect but also by the acceptor ionization effect. In addition, the phonon lifetimes were calculated via the energy-time uncertainty relation and the phonon decay mechanisms were illustrated. Furthermore, with temperature rising, the change of Raman scattering intensity was discussed.