The first- and second-order Raman scattering and IR reflection have been studied for hexagonal InN layers grown on (0001) and (102)
sapphire substrates. All six Raman-active optical phonons were observed and assigned: E2(low)
at 87 cm−1, E2(high)
at 488 cm−1, A1(TO)
at 447 cm−1, E1(TO)
at 476 cm−1, A1(LO)
at 586 cm−1,
at 593 cm−1.
The ratio between the InN static dielectric constants for the ordinary and extraordinary directions was found to be ε⊥0/ε∥0 = 0.91.
The phonon dispersion curves, phonon density-of-state function, and lattice specific heat were calculated. The Debye temperature at 0 K for hexagonal InN was estimated to be 370 K. © 1999 American Institute of Physics.