Influence of electron-phonon interaction on the optical properties of III nitride semiconductors

The electronic band structures of III nitride semiconductors calculated wit hin the adiabatic approximation give essential information about the optica l properties of materials. However, atoms of the lattice are not at rest; t heir displacement away from the equilibrium positions perturbs the periodic potential acting on the electrons in the crystal, leading to an electron-p honon interaction energy. Due to different ways that the lattice. vibration perturbs the motions of electrons, there are various types of interaction, such as Frohlich interaction with longitudinal optical phonons, deformatio n-potential interactions with optical and acoustic phonons and piezoelectri c interaction with acoustic phonons. These interactions, especially the Fro hlich interaction, which is very strong due to the ionic nature of III nitr ides, have a great influence on the optical properties of the III nitride s emiconductors. As a result of electron-phonon interaction, several phenomen a, such as phonon replicas in the emission spectra, homogeneous broadening of the excitonic line width and the relaxation of hot carriers to the funda mental band edge, which have been observed in GaN and its low dimensional h eterostructures, are reviewed.