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Anisotropy-induced polarization mixture of surface acoustic waves in GaN/c -sapphire heterostructures

Anisotropy-induced polarization mixture of surface acoustic waves in GaN/c -sapphire heterostructures,10.1103/PhysRevB.72.075306,Physical Review B,J.

Anisotropy-induced polarization mixture of surface acoustic waves in GaN/c -sapphire heterostructures   (Citations: 4)
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The characteristics of surface acoustic waves (SAWs) in GaN layers grown on c -plane sapphire are investigated. Besides Rayleigh mode, Sezawa and Love modes, which are confined in the nitride layers, arise because of the slow sound propagation in GaN compared with the substrate. In addition, pseudo-SAWs leaking into the bulk are observed. The trigonal crystal symmetry of sapphire not only leads to an anisotropic propagation of the SAWs in the heterostructures, despite the isotropic elastic properties in the c -plane GaN, but also mixes their polarization even for the propagation along high-crystal-symmetry directions. Love modes, which are normally piezoelectrically inactive, can be excited by interdigital transducers through this polarization mixture. The nonzero value of the elastic coefficient c14 of sapphire is indicated to be the origin of the coupling of sagittal and shear horizontal displacements.
Journal: Physical Review B - PHYS REV B , vol. 72, no. 7, 2005
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    • ...Sezawa or lossy pseudobulk modes, reported in [7] and [8], for GaN/sapphire have not been observed...

    Alexandru Mulleret al. SAW Devices Manufactured on GaN/Si for Frequencies Beyond 5 GHz

    • ...In group-III nitride layers on (0001) sapphire substrates, due to the difference in elastic properties between the two materials, several SAW modes with different profiles of displacements and different velocities emerge [10]...
    • ...GaN layers were insulating (insulator model), we calculated the transport characteristics of SAWs, such as their dispersion of velocity and spatial distribution of energy, in GaN layers propagating along the � 1¯� direction of sapphire substrates by using the transfer matrix approach [10], [20]...
    • ...We used reported values for the mass density ρ, the elastic constant Cijkl, the dielectric constant � ij, and the piezoelectric coefficient eijk for GaN and sapphire [4], [10]...

    Naoteru Shigekawaet al. Surface Acoustic Waves in Reverse-Biased AlGaN/GaN Heterostructures

    • ...The first Sezawa and Love modes were identified in Fig. 4, according to the calculated dispersion relations in a GaN/Sapphire layered structure [11]...

    King-Yuen Wonget al. Two-dimensional electron gas (2DEG) IDT SAW devices on AlGaN/GaN heter...

    • ...The identification of the modes is based on the GaN/sapphire dispersion curves in [6], since the AlGaN layer thickness is negligible compared to that of the GaN layer (∼7.6 µm) and the IDT period...
    • ...The analysis presented in this work corresponds to the modes propagating in the [1-100] direction...

    J. Pedroset al. 6C-3 Field-Effect-Modulated SAW Devices on AlGaN/GaN Heterostructures

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