Phonons in hexagonal InN. Experiment and theory

We present the results of a detailed study of the first- and second-order R aman scattering and IR reflection from hexagonal InN layers grown on (0001) and (1 (1) over bar 02) sapphire substrates. All six Raman active optical phonons were measured and assigned: E-2(low) at 87 cm(-1), E-2(high) at 488 cm(-1), A(1)(TO) at 447 cm(-1), E-1(TO) at 476 cm(-1), A(1)(LO) at 586 cm( -1), and E-1(LO) at 593 cm(-1). The static dielectric constants of InN for the ordinary and extraordinary directions were estimated to be epsilon(perp endicular to 0) = 13.1 and epsilon(\\0) = 14.4, respectively. The phonon di spersion curves and phonon density-of-state function for hexagonal InN were calculated by scanning throughout the BZ.