GaN films of different buffer thicknesses (from 0 to 600 Angstrom) wer
e grown on (0001) sapphire using MOCVD. The epitaxial films show autod
oping with carrier concentration ranging from 8 x 10(16) to 5 x 10(17)
cm(-3) as determined by Hall measurements. The Raman scattering revea
ls that the A(1)(LO) mode shifts from 733 to 740 cm(-1) as a result of
the phonon-plasmon interaction.