Composition dependence of optical phonon energies and Raman line broadening in hexagonal<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">Al</mml:mi></mml:mrow><mml:mrow><mml:mi>x</mml:mi></mml:mrow></mml:msub></mml:mrow><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">Ga</mml:mi></mml:mrow><mml:mrow><mml:mn>1</mml:mn><mml:mi>−</mml:mi><mml:mi>x</mml:mi></mml:mrow></mml:msub></mml:mrow><mml:mi mathvariant="normal">

Davydov, V. Yu.; Goncharuk, I. N.; Смирнов, А. Н.; Николаев, А. Е.; Lundin, W. V.; Usikov, A. S.; Klochikhin, A. A.; Aderhold, J.; Graul, J.; Semchinova, O.; Harima, Hiroshi

doi:10.1103/physrevb.65.125203

Cited by 150 publications

(107 citation statements)

References 40 publications

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“…The frequencies of the modes observed are compatible with those reported in the literature, for example in Ref. 10 improved signal-to-noise ratio in the temperature measurement). For Al x Ga 1Àx N, the E 2 mode splits into AlN-like and GaN-like lines, which share the intensity in approximate proportion to the Al fraction, for example, for Al 0.18 Ga 0.82 N the GaN-like mode is much stronger than the AlN-like mode, which is even not observable, and correspondingly for the other layers.…”

supporting

confidence: 81%

“…Broadening for Al x Ga 1Àx N Raman modes due to alloy disorder is observed for both E 2 and A 1 , compatible with that reported by Davydov. 10 For calibration, thermal peak shifts for Raman-accessible phonon modes were determined as a function of temperature (inset to Figure 2) using backplate heating/cooling of the whole device. The thermal characteristics of the device were simulated in three dimensions using Thermal Analysis System (TAS) finite difference software from Ansys, Inc. As Raman thermography measures average temperature over each device layer thickness, 11 the temperature in the simulation was averaged over a volume corresponding to the laser focus within each layer when comparing to experimental data.…”

mentioning

confidence: 99%

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AlGaN/GaN field effect transistors for power electronics—Effect of finite GaN layer thickness on thermal characteristics

Hodges

Calvo

Stoffels

et al. 2013

Applied Physics Letters

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AlGaN/GaN heterostructure field effect transistors with a 150 nm thick GaN channel within stacked AlxGa1−xN layers were investigated using Raman thermography. By fitting a thermal simulation to the measured temperatures, the thermal conductivity of the GaN channel was determined to be 60 W m−1 K−1, over 50% less than typical GaN epilayers, causing an increased peak channel temperature. This agrees with a nanoscale model. A low thermal conductivity AlGaN buffer means the GaN spreads heat; its properties are important for device thermal characteristics. When designing power devices with thin GaN layers, as well as electrical considerations, the reduced channel thermal conductivity must be considered.

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supporting

confidence: 81%

mentioning

confidence: 99%

AlGaN/GaN field effect transistors for power electronics—Effect of finite GaN layer thickness on thermal characteristics

Hodges

Calvo

Stoffels

et al. 2013

Applied Physics Letters

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“…In Ref. 10, a similar observation in In x Ga 1Àx N films with x < 0.5 led the authors to conclude that the E 2h mode exhibits a two-mode behavior, as occurs in Al x Ga 1Àx N. 40 In the present work, using data over the whole composition range, we conclude that the E 2h mode of In x Ga 1Àx N exhibits a one-mode behavior and suffers a strong bowing effect. Very recent work by Kim et al 21 seems to point in the same direction.…”

Section: -4supporting

confidence: 50%

Raman scattering by the E2h and A1(LO) phonons of InxGa1−xN epilayers (0.25 < x < 0.75) grown by molecular beam epitaxy

Oliva

Ibáñez

Cuscó

et al. 2012

Journal of Applied Physics

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We use Raman scattering to investigate the composition behavior of the E 2h and A 1 (LO) phonons of In x Ga 1Àx N and to evaluate the role of lateral compositional fluctuations and in-depth strain/ composition gradients on the frequency of the A 1 (LO) bands. For this purpose, we have performed visible and ultraviolet Raman measurements on a set of high-quality epilayers grown by molecular beam epitaxy with In contents over a wide composition range (0.25 < x < 0.75). While the as-measured A 1 (LO) frequency values strongly deviate from the linear dispersion predicted by the modified random-element isodisplacement (MREI) model, we show that the strain-corrected A 1 (LO) frequencies are qualitatively in good agreement with the expected linear dependence. In contrast, we find that the strain-corrected E 2h frequencies exhibit a bowing in relation to the linear behavior predicted by the MREI model. Such bowing should be taken into account to evaluate the composition or the strain state of InGaN material from the E 2h peak frequencies. We show that in-depth strain/composition gradients and selective resonance excitation effects have a strong impact on the frequency of the A 1 (LO) mode, making very difficult the use of this mode to evaluate the strain state or the composition of InGaN material. V C 2012 American Institute of Physics.

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“…Here, d 31 , d 33 and d 51 are known as the piezoelectric coefficients found in the wurtzite crystal structure. 7 In any 3D coordinate system, each mutually independent element in the piezoelectric third rank tensor depends only on the crystallographic structure and orientations of the material.…”

Section: The Domain Switching In the Piezoelectric Zones Of Algan Micmentioning

confidence: 99%

“…Because of the polar nature of the unit cell, A 1 and E 1 modes can again split into longitudinal optical (LO) and transverse optical (TO) modes. Therefore, there are six optical modes 31 In order to understand the compositional homogeneity and crystalline nature of the pristine AlGaN microrod, we carried out a Raman imaging of the integrated intensity distribution of H E 2 mode along one isolated crystal (supplementary Fig. S6).…”

mentioning

confidence: 99%

Piezoelectric domains in the AlGaN hexagonal microrods: Effect of crystal orientations

Sivadasan

Mangamma

Bera

et al. 2016

Journal of Applied Physics

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Presently, the piezoelectric materials are finding tremendous applications in the micro-mechanical actuators, sensors and self-powered devices. In this context, the studies pertaining to piezoelectric properties of materials in the different size ranges are very important for the scientific community. The III-nitrides are exceptionally important, not only for optoelectronic but also for their piezoelectric applications. In the present study, we synthesized AlGaN via self catalytic vapor-solid mechanism by atmospheric pressure chemical vapor deposition technique on AlN base layer over intrinsic Si(100) substrate. The growth process is substantiated using X-ray diffraction and X-ray photoelectron spectroscopy. The Raman and photoluminescence study reveal the formation of AlGaN microrods in the wurtzite phase and ensures the high optical quality of the crystalline material. The single crystalline, direct wide band gap and hexagonally shaped AlGaN microrods are studied for understanding the behavior of the crystallites under the application of constant external electric field using the piezoresponse force microscopy. The present study is mainly focused on understanding the behavior of induced polarization for the determination of piezoelectric coefficient of AlGaN microrod along the c-axis and imaging of piezoelectric domains in the sample originating because of the angular inclination of AlGaN microrods with respect to its AlN base layers.2

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Composition dependence of optical phonon energies and Raman line broadening in hexagonalAlxGa1−x

Cited by 150 publications

References 40 publications

AlGaN/GaN field effect transistors for power electronics—Effect of finite GaN layer thickness on thermal characteristics

AlGaN/GaN field effect transistors for power electronics—Effect of finite GaN layer thickness on thermal characteristics

Raman scattering by the E2h and A1(LO) phonons of InxGa1−xN epilayers (0.25 < x < 0.75) grown by molecular beam epitaxy

Piezoelectric domains in the AlGaN hexagonal microrods: Effect of crystal orientations

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Composition dependence of optical phonon energies and Raman line broadening in hexagonalAlxGa1−x

Cited by 150 publications

References 40 publications

AlGaN/GaN field effect transistors for power electronics—Effect of finite GaN layer thickness on thermal characteristics

AlGaN/GaN field effect transistors for power electronics—Effect of finite GaN layer thickness on thermal characteristics

Raman scattering by the E2h and A1(LO) phonons of InxGa1−xN epilayers (0.25 &lt; x &lt; 0.75) grown by molecular beam epitaxy

Piezoelectric domains in the AlGaN hexagonal microrods: Effect of crystal orientations

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Raman scattering by the E2h and A1(LO) phonons of InxGa1−xN epilayers (0.25 < x < 0.75) grown by molecular beam epitaxy