Anharmonic effects in the phonons of III–V semiconductors: first principles calculations

We present an ab initio calculation of the real part of the phonon self energy for longitudinal and transverse optical Raman phonons in GaAs, AlAs, GaP and InP. The calculated temperature dependences of transverse and longitudinal modes at the Γ-point are in good agreement with available experimental data. This calculation permits us to analyze the different contributions to the real part of the phonon self-energy. In particular we are able to reproduce the observed asymmetry of the Raman line of the transverse optical mode in GaP. Furthermore, we explain why the frequency of this mode changes less with temperature than that of the transverse mode in the other materials investigated. The pressure dependence of the real and the imaginary parts of the phonon self-energy are also discussed.