We report on first studies of the phonon mode properties of hexagonal AlxInyGa1-x-yN films. The 200-330 nm thick quaternary films (0 ≤ x ≤ 0.40, y ≈ 0.12), grown by MOCVD on 6H-SiC substrates, are pseudomorphically strained to the GaN buffer layers. We observe and differentiate the influence of strain and alloying on the frequency of the GaN-like E1(TO) phonon mode of AlxInyGa1-x-yN using infrared spectroscopic ellipsometry. Assuming the effective electron mass value of GaN, the free-electron concentrations are estimated from the A1-LO-phonon-plasmon coupled mode frequencies and increase by about two orders of magnitude in going from x = 0 to x = 0.40. We further obtain the composition dependence of the polarity for the AlN-like phonon mode with E1 symmetry. A possibly disorder-induced absorption band occurs above the GaN-like E1(TO) mode.
|Original language||English (US)|
|Number of pages||5|
|Journal||Physica Status Solidi (B) Basic Research|
|State||Published - Dec 1 2002|
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Condensed Matter Physics