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

M. Schubert, A. Kasic, T. E. Tiwald, J. A. Woollam, V. Harle, F. Scholz

Research output: Contribution to journalArticle

1 Scopus citations

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 - 2000

ASJC Scopus subject areas

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

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