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.