Phonons and free carriers in a strained hexagonal GaN-AlN 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 journalConference article

2 Scopus citations

Abstract

Phonon and free-carrier effects in a strained hexagonal (α) {GaN}l-{AlN}m superlattice (SL) heterostructure (l = 8 nm, m = 3 nm) are studied by infrared spectroscopic ellipsometry (IRSE) and micro (μ)-Raman scattering. Growth of the heterostructures was performed by metal-organic vapor phase epitaxy (MOVPE) on (0001) sapphire. An unstrained 1 μm-thick α-GaN layer was deposited prior to the SL. SL phonon modes are identified combining results from both IRSE and μ-Raman techniques. The shift of the GaN-sublayer phonon modes is used to estimate an average compressive SL stress of σxx approx. -4.3 GPa. The IRSE data reveal a free-carrier concentration of ne approx. 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 (μ approx. 400 cm2/Vs, polarization E⊥c-axis) exceeds the vertical mobility (μ approx. 24 cm2/Vs, E∥c) by one order of magnitude.

Original languageEnglish (US)
Pages (from-to)W11.39.1 - W11.39.6
JournalMaterials Research Society Symposium - Proceedings
Volume595
StatePublished - 2000
EventThe 1999 MRS Fall Meeting - Symposium W 'GaN and Related Alloys' - Boston, MA, USA
Duration: Nov 28 1999Dec 3 1999

ASJC Scopus subject areas

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

Fingerprint Dive into the research topics of 'Phonons and free carriers in a strained hexagonal GaN-AlN superlattice measured by infrared ellipsometry and Raman spectroscopy'. Together they form a unique fingerprint.

  • Cite this