Metal/semiconductor superlattices represent a fascinating frontier in materials science and nanotechnology, where alternating layers of metals and semiconductors are precisely engineered at the atomic and nano-scales. Traditionally, epitaxial metal/semiconductor superlattice growth requires constituent materials from the same family, exhibiting identical structural symmetry and low lattice mismatch. Here, beyond this conventional constraint, a novel class of epitaxial lattice-matched metal/semiconductor superlattices is introduced that utilizes refractory hexagonal elemental transition metals and wide-bandgap III-nitride semiconductors. Exemplified by the Hf/AlN superlattices exhibiting coherent layer-by-layer epitaxial growth, cross-plane thermionic emission is observed through current–voltage measurements accomplished for the first time in any metal/semiconductor superlattices. Further, thermoreflectance measurements reveal significant enhancement in cross-plane Seebeck coefficients attributed to carrier energy filtering by Schottky barriers. Demonstration of artificially structured elemental-metal/wide-bandgap compound-semiconductor superlattices promises to usher in new fundamental physics studies and cutting-edge applications such as tunable hyperbolic metamaterials, quantum computing, and thermionic-emission-based thermoelectric and thermophotonic energy conversion devices.

中文翻译：

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人工结构的单晶元素金属/化合物半导体超晶格中的热电子发射


金属/半导体超晶格代表了材料科学和纳米技术中一个迷人的前沿领域，其中金属和半导体的交替层在原子和纳米尺度上被精确设计。传统上，外延金属/半导体超晶格生长需要来自同一家族的组成材料，表现出相同的结构对称性和低晶格失配。在这里，超越了这个常规约束，引入了一类新型的外延晶格匹配金属/半导体超晶格，它利用难熔六方元素过渡金属和宽带隙 III 氮化物半导体。以表现出相干逐层外延生长的 Hf/AlN 超晶格为例，通过首次在任何金属/半导体超晶格中完成的电流-电压测量来观察到跨平面热电子发射。此外，热反射测量揭示了肖特基势垒对载流子能量滤波的跨平面塞贝克系数的显著增强。人工结构的元素金属/宽带隙化合物-半导体超晶格的演示有望迎来新的基础物理研究和前沿应用，例如可调谐双曲超材料、量子计算以及基于热电子发射的热电和热光子能量转换器件。