Unveiling Phonon Dispersion Behavior of AlN/GaN Heterostructures Using EELS

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Abstract
III-V semiconductor heterostructures are commonly used in modern electronic devices due to their bandgap tunability, high electron mobility and thermal stability [ 1].These heterostructures are made of different semiconductor layers forming one (i.e., single junction) or several interfaces (i.e., quantum well structure). Lattice vibrations (phonons) at those interfaces play a key role in heat dissipation and electron mobility processes [ 1, 2]. The study of interface phonon properties requires the use of nanoscale-sized probes to characterize its local response. Thanks to the development of novel technologies for monochromators and spectrometers, atom-wide monochromatic probes have become available in electron microscopes, thus offering vibrational scattering information over a wide spectral section of the infrared range with an unmatched spatial sensitivity [ 3]. For instance, inelastic phonon scattering from nanomaterials can be obtained in the real [ 4] and reciprocal spaces[ 5]. We present a momentum-resolved EELS study of the phonon dispersion across AlN/GaN interfaces using a nanometer-sized electron probe.