Raman selection rules in C6v4 hexagonal crystals: Allowed combinations and overtones of vibrational modes in wurtzite GaN

Abstract

A discrete set of oscillators belongs to the critical points in the lattice vibration spectrum. The vibrational states of crystals are classified according to appropriate irreducible representations of the relevant wave vector space groups. Suitable space-group selection rules are used to determine the active one and two phonon combinations and overtone processes in hexagonal structures. Experimental Raman spectra of the hexagonal C6v4 GaN are discussed in terms of the derived selection rules.