ScxAl1−xN (x = 0.18–0.40) thin films of ∼28 nm thickness grown on metal polar GaN substrates by molecular beam epitaxy are found to exhibit smooth morphology with less than 0.5 nm roughness and predominantly single-phase wurtzite crystal structure throughout the composition range. Measurement of the piezoelectric d33 coefficient shows a 150% increase for lattice-matched Sc0.18Al0.82N relative to pure aluminum nitride, whereas higher Sc contents exhibit lower piezoelectric coefficients. The electromechanical response of the epitaxial films correlates with the crystal quality and the presence of zinc blende inclusions, as observed by high-resolution electron microscopy. It is further found that the polarity of the epitaxial ScxAl1−xN layers is locked to the underlying substrate. The measured electromechanical properties of epitaxial ScxAl1−xN, their relation to the atomic crystal structure and defects, and its crystal polarity provide useful guidance toward the applications of this material.

中文翻译：

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通过分子束外延在 GaN 上生长的超薄 ScxAl1-xN 薄膜的结构和压电性能

ScxAl1−xN (x = 0.18–0.40) 通过分子束外延在金属极性 GaN 衬底上生长的厚度约为 28 nm 的薄膜表现出光滑的形态，粗糙度小于 0.5 nm，整个组合物中主要是单相纤锌矿晶体结构范围。压电 d33 系数的测量表明，与纯氮化铝相比，晶格匹配的 Sc0.18Al0.82N 增加了 150%，而较高的 Sc 含量表现出较低的压电系数。通过高分辨率电子显微镜观察，外延膜的机电响应与晶体质量和闪锌矿夹杂物的存在相关。进一步发现外延 ScxAl1-xN 层的极性锁定在下面的衬底上。外延 ScxAl1−xN 的测量机电性能，