Phonons and free carriers in strained hexagonal GaN/AlGaN superlattices measured by infrared ellipsometry and Raman spectroscopy

M. Schubert, A. Kasic, J. Šik, S. Einfeldt, D. Hommel, V. Härle, J. Off, F. Scholz

Research output: Contribution to journalArticle

12 Citations (Scopus)

Abstract

Phonon and free-carrier effects in strained hexagonal (α) {GaN}l-{AlxGa1-xN}m superlattice (SL) heterostructures 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) and molecular beam epitaxy on (0001) sapphire. Unstrained 0.5-1 μm-thick α-GaN layers were deposited prior to the SLs. SL phonon modes are identified combining results from both IRSE and μ-Raman techniques. The average compressive SL stress can be estimated from the shift of the GaN-sublayer phonon modes. The IRSE data are sensitive to free carriers within the GaN sublayers. For the MOVPE grown SL structures, the free-carrier mobility is anisotropic which indicates vertical carrier confinement.

Original languageEnglish (US)
Pages (from-to)178-181
Number of pages4
JournalMaterials Science and Engineering B: Solid-State Materials for Advanced Technology
Volume82
Issue number1-3
DOIs
StatePublished - May 22 2001

Fingerprint

Spectroscopic ellipsometry
Ellipsometry
Superlattices
Phonons
ellipsometry
superlattices
Raman spectroscopy
phonons
Vapor phase epitaxy
Infrared radiation
vapor phase epitaxy
Heterojunctions
Metals
spectroscopy
Aluminum Oxide
Carrier mobility
carrier mobility
Compressive stress
Molecular beam epitaxy
Sapphire

Keywords

  • AlGaN
  • Ellipsometry
  • Infrared
  • Optical properties
  • Strain
  • Superlattice phonons

ASJC Scopus subject areas

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

Cite this

Phonons and free carriers in strained hexagonal GaN/AlGaN superlattices measured by infrared ellipsometry and Raman spectroscopy. / Schubert, M.; Kasic, A.; Šik, J.; Einfeldt, S.; Hommel, D.; Härle, V.; Off, J.; Scholz, F.

In: Materials Science and Engineering B: Solid-State Materials for Advanced Technology, Vol. 82, No. 1-3, 22.05.2001, p. 178-181.

Research output: Contribution to journalArticle

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T1 - Phonons and free carriers in strained hexagonal GaN/AlGaN superlattices measured by infrared ellipsometry and Raman spectroscopy

AU - Schubert, M.

AU - Kasic, A.

AU - Šik, J.

AU - Einfeldt, S.

AU - Hommel, D.

AU - Härle, V.

AU - Off, J.

AU - Scholz, F.

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N2 - Phonon and free-carrier effects in strained hexagonal (α) {GaN}l-{AlxGa1-xN}m superlattice (SL) heterostructures 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) and molecular beam epitaxy on (0001) sapphire. Unstrained 0.5-1 μm-thick α-GaN layers were deposited prior to the SLs. SL phonon modes are identified combining results from both IRSE and μ-Raman techniques. The average compressive SL stress can be estimated from the shift of the GaN-sublayer phonon modes. The IRSE data are sensitive to free carriers within the GaN sublayers. For the MOVPE grown SL structures, the free-carrier mobility is anisotropic which indicates vertical carrier confinement.

AB - Phonon and free-carrier effects in strained hexagonal (α) {GaN}l-{AlxGa1-xN}m superlattice (SL) heterostructures 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) and molecular beam epitaxy on (0001) sapphire. Unstrained 0.5-1 μm-thick α-GaN layers were deposited prior to the SLs. SL phonon modes are identified combining results from both IRSE and μ-Raman techniques. The average compressive SL stress can be estimated from the shift of the GaN-sublayer phonon modes. The IRSE data are sensitive to free carriers within the GaN sublayers. For the MOVPE grown SL structures, the free-carrier mobility is anisotropic which indicates vertical carrier confinement.

KW - AlGaN

KW - Ellipsometry

KW - Infrared

KW - Optical properties

KW - Strain

KW - Superlattice phonons

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