Phonons and free carriers in a strained hexagonal GaN-AIN superlattice measured by infrared ellipsometry and raman spectroscopy

Mathias Schubert, A. Kasic, T. E. Tiwald, John A Woollam, V. Harle, F. Scholz

Research output: Contribution to journalArticle

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Abstract

Phonon and free-carrier effects in a strained hexagonal (α) (GaN)/-(A1N)m, superlattice (SL) heterostructure (/ = 8 nm, i = 3 nm) are studied by infrared spectroscopic ellipsometry (IRSE) and micro (n)-Raman scattering. Growth of the heterostructures was performed by metal-organic vapor phase epitaxy (MOVPE) on (0001) sapphire. An unstrained 1 urn-thick or-GaN layer was deposited prior to the SL. SL phonon modes are identified combining results from both IRSE and |a-Raman techniques. The shift of the GaN-sublayer phonon modes is used to estimate an average compressive SL stress of σxx ∼ - 4.3 GPa. The IRSE data reveal a free-carrier concentration of ne ∼ 5×1018 cm-3 within the undoped SL GaN-sublayers. According to the vertical carrier confinement, the free-carrier mobility is anisotropic, and the lateral mobility (//j. - 400 cmWs, polarization £lr-axis) exceeds the vertical mobility (jit 24 cm2/Vs, £llc) by one order of magnitude.

Original languageEnglish (US)
Pages (from-to)W11391-W11396
JournalMaterials Research Society Symposium - Proceedings
Volume595
DOIs
StatePublished - Jan 1 2000

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Spectroscopic ellipsometry
Ellipsometry
Phonons
ellipsometry
Raman spectroscopy
phonons
Infrared radiation
Heterojunctions
spectroscopy
Vapor phase epitaxy
Aluminum Oxide
Carrier mobility
carrier mobility
Compressive stress
Sapphire
vapor phase epitaxy
Carrier concentration
Raman scattering
sapphire
Metals

ASJC Scopus subject areas

  • Materials Science(all)
  • Condensed Matter Physics
  • Mechanics of Materials
  • Mechanical Engineering

Cite this

Phonons and free carriers in a strained hexagonal GaN-AIN superlattice measured by infrared ellipsometry and raman spectroscopy. / Schubert, Mathias; Kasic, A.; Tiwald, T. E.; Woollam, John A; Harle, V.; Scholz, F.

In: Materials Research Society Symposium - Proceedings, Vol. 595, 01.01.2000, p. W11391-W11396.

Research output: Contribution to journalArticle

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AU - Scholz, F.

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