Characterization of single-crystalline GaAs by imaging with ballistic phonons |
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Authors: | E Held W Klein R P Huebener |
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Institution: | (1) Physikalisches Institut, Lehrstuhl Experimentalphysik II, Universität Tübingen, Auf der Morgenstelle 14, D-7400 Tübingen, Federal Republic of Germany |
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Abstract: | Ballistic phonon propagation in single-crystalline 001]-oriented gallium arsenide has been studied using low-temperature scanning electron microscopy for imaging. Deviations in the phonon focusing pattern due to dispersion effects were found by comparing the phonon images to theoretical calculations of the long-wavelength limit. The phonon propagation behavior in, samples cut from differently prepared wafers has been investigated. For highly impure crystals we found a pronounced increase of the diffusive signal component at the expense of the ballistic one. Samples with varying dislocation densities also showed a sensitive dependence, of the ballistic phonon propagation on these crystal defects. For focusing calculations considering elastic scattering processes the diffusivity of the phonons could be determined as a function of the mean scattering length. We have found phonon mean free paths of 0.35 mm to 0.80 mm for the various GaAs crystals. |
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