Phonons and free carriers in a strained hexagonal GaN-AlN superlattice measured by infrared ellipsometry and Raman spectroscopy
Phonon and free-carrier effects in a strained hexagonal ({alpha}) {l_brace}GaN{r_brace}{sub l}--{l_brace}AlN{r_brace}{sub m} superlattice (SL) heterostructure (l = 8 nm, m = 3 nm) are studied by infrared spectroscopic ellipsometry (IRSE) and micro ({micro})-Raman scattering. Growth of the heterostructures was performed by metal-organic vapor phase epitaxy (MOVPE) on (0001) sapphire. An unstrained 1 {micro}m-thick {alpha}-GaN layer was deposited prior to the SL. SL phonon modes are identified combining results from both IRSE and {micro}-Raman techniques. The shift of the GaN-sublayer phonon modes is used to estimate an average compressive SL stress of {sigma}{sub xx} {approximately} {minus}4.3 GPa. The IRSE data reveal a free-carrier concentration of n{sub e} {approximately} 5x10{sup 18} cm{sup {minus}3} within the undoped SL GaN-sublayers. According to the vertical carrier confinement, the free-carrier mobility is anisotropic, and the lateral mobility ({mu}{sub {perpendicular}} {approximately} 400 cm{sup 2}/Vs, polarization E{perpendicular}c-axis) exceeds the vertical mobility ({mu}{sub {parallel}} {approximately} 24 cm{sup 2}/Vs, E{parallel}c) by one order of magnitude.
- Research Organization:
- Univ. of Nebraska, Lincoln, NE (US)
- OSTI ID:
- 20104609
- Resource Relation:
- Conference: 1999 Materials Research Society Fall Meeting, Boston, MA (US), 11/28/1999--12/03/1999; Other Information: PBD: 2000; Related Information: In: GaN and related alloys -- 1999. Materials Research Society symposium proceedings, Volume 595, by Myers, T.H.; Feenstra, R.M.; Shur, M.S.; Amano, Hiroshi [eds.], [1050] pages.
- Country of Publication:
- United States
- Language:
- English
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