Systematic measurements by light scattering of the linewidth and frequency shift of the $\overrightarrow{\mathrm{q}}=0\mathrm{}$ optical phonon in silicon over the temperature range of 5-1400 K are presented. Both the linewidth and frequency shift exhibit a quadratic dependence on temperature at high temperatures. This indicates the necessity of including terms in the phonon proper self-energy corresponding to four-phonon anharmonic processes.

• Received 13 July 1982

DOI:https://doi.org/10.1103/PhysRevB.28.1928