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

doi:10.1557/PROC-595-F99W11.39

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

Electrical & Computer Engineering

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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 σ_xx ∼ - 4.3 GPa. The IRSE data reveal a free-carrier concentration of n_e ∼ 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 language	English (US)
Pages (from-to)	W11391-W11396
Journal	Materials Research Society Symposium - Proceedings
Volume	595
DOIs	https://doi.org/10.1557/PROC-595-F99W11.39
State	Published - 2000

ASJC Scopus subject areas

General Materials Science
Condensed Matter Physics
Mechanics of Materials
Mechanical Engineering

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

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.",

author = "M. Schubert and A. Kasic and Tiwald, {T. E.} and Woollam, {J. A.} and V. Harle and F. Scholz",

year = "2000",

doi = "10.1557/PROC-595-F99W11.39",

language = "English (US)",

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pages = "W11391--W11396",

journal = "Materials Research Society Symposium - Proceedings",

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TY - JOUR

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

AU - Schubert, M.

AU - Kasic, A.

AU - Tiwald, T. E.

AU - Woollam, J. A.

AU - Harle, V.

AU - Scholz, F.

PY - 2000

Y1 - 2000

N2 - 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.

AB - 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.

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

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