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. Härle, F. Scholz

Research output: Contribution to journalArticle

3 Citations (Scopus)

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 ∼ - 4.3 GPa. The IRSE data reveal a free-carrier concentration of ne ∼ 5×10 18 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 ∼ 400 cm2/Vs, polarization E⊥c-axis) exceeds the vertical mobility (μ ∼ 24 cm2/Vs, E∥c) by one order of magnitude.

Original languageEnglish (US)
JournalMRS Internet Journal of Nitride Semiconductor Research
Volume5
Issue numberSUPPL. 1
StatePublished - Dec 1 2000

Fingerprint

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

ASJC Scopus subject areas

  • Materials Science(all)

Cite this

Phonons and free carriers in a strained hexagonal GaN-AlN superlattice measured by infrared ellipsometry and Raman spectroscopy. / Schubert, M.; Kasic, A.; Tiwald, T. E.; Woollam, J. A.; Härle, V.; Scholz, F.

In: MRS Internet Journal of Nitride Semiconductor Research, Vol. 5, No. SUPPL. 1, 01.12.2000.

Research output: Contribution to journalArticle

@article{3f6409d6329e407281545c3131aea569,
title = "Phonons and free carriers in a strained hexagonal GaN-AlN superlattice measured by infrared ellipsometry and Raman spectroscopy",
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 ∼ - 4.3 GPa. The IRSE data reveal a free-carrier concentration of ne ∼ 5×10 18 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⊥ ∼ 400 cm2/Vs, polarization E⊥c-axis) exceeds the vertical mobility (μ∥ ∼ 24 cm2/Vs, E∥c) by one order of magnitude.",
author = "M. Schubert and A. Kasic and Tiwald, {T. E.} and Woollam, {J. A.} and V. H{\"a}rle and F. Scholz",
year = "2000",
month = "12",
day = "1",
language = "English (US)",
volume = "5",
journal = "MRS Internet Journal of Nitride Semiconductor Research",
issn = "1092-5783",
publisher = "Materials Research Society",
number = "SUPPL. 1",

}

TY - JOUR

T1 - Phonons and free carriers in a strained hexagonal GaN-AlN superlattice measured by infrared ellipsometry and Raman spectroscopy

AU - Schubert, M.

AU - Kasic, A.

AU - Tiwald, T. E.

AU - Woollam, J. A.

AU - Härle, V.

AU - Scholz, F.

PY - 2000/12/1

Y1 - 2000/12/1

N2 - 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 ∼ - 4.3 GPa. The IRSE data reveal a free-carrier concentration of ne ∼ 5×10 18 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⊥ ∼ 400 cm2/Vs, polarization E⊥c-axis) exceeds the vertical mobility (μ∥ ∼ 24 cm2/Vs, E∥c) by one order of magnitude.

AB - 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 ∼ - 4.3 GPa. The IRSE data reveal a free-carrier concentration of ne ∼ 5×10 18 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⊥ ∼ 400 cm2/Vs, polarization E⊥c-axis) exceeds the vertical mobility (μ∥ ∼ 24 cm2/Vs, E∥c) by one order of magnitude.

UR - http://www.scopus.com/inward/record.url?scp=0010677042&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=0010677042&partnerID=8YFLogxK

M3 - Article

AN - SCOPUS:0010677042

VL - 5

JO - MRS Internet Journal of Nitride Semiconductor Research

JF - MRS Internet Journal of Nitride Semiconductor Research

SN - 1092-5783

IS - SUPPL. 1

ER -