基于二维冷金属的高峰谷电流比 NDR 隧道二极管的计算设计：NbSi$_2$N$_4$/HfSi$_2$N$_4$/NbSi$_2$N$_4$ 横向异质结二极管案例
Computational design of NDR tunnel diodes with high peak-to-valley current ratio based on two-dimensional cold metals: The case of NbSi$_2$N$_4$/HfSi$_2$N$_4$/NbSi$_2$N$_4$ lateral heterojunction diode
AI总结：
该研究利用 DFT 与非平衡 Green 函数方法模拟 NbSi$_2$N$_4$/HfSi$_2$N$_4$ 横向异质结，揭示取向和势垒厚度对 NDR 隧道二极管峰值电流与 PVCR 的调控作用。
摘要：
冷金属近来作为创新器件的理想平台受到关注，例如具有负微分电阻（NDR）的隧道二极管，以及亚阈值摆幅低于热离子极限的场效应晶体管。近期发现的二维（2D）MA$_2$Z$_4$（M = Ti、Zr、Hf、Nb、Ta；A = Si、Ge；Z = N、P）化合物同时表现出冷金属性和半导体性行为。在本工作中，我们对基于二维 NbSi$_2$N$_4$ 与 HfSi$_2$N$_4$ 化合物的横向异质结隧道二极管进行了计算研究。我们采用密度泛函理论结合非平衡 Green 函数方法，研究了在 zigzag 和 armchair 两种取向下、具有不同势垒厚度的横向隧道二极管的电流-电压（$I$-$V$）特性。我们发现，zigzag 取向的隧道二极管表现出显著更高的峰值电流密度，而与 zigzag 取向相比，armchair 取向的隧道二极管则呈现更大的峰谷电流比（PVCR）。研究结果表明，MA$_2$Z$_4$ 材料是实现具有高 PVCR 值的 NDR 隧道二极管的有前景候选材料，这类二极管在存储器、逻辑电路及其他电子器件中具有潜在应用。
英文摘要：
Cold metals have recently gained attention as a promising platform for innovative devices, such as tunnel diodes with negative differential resistance (NDR) and field-effect transistors with subthreshold swings below the thermionic limit. Recently discovered two-dimensional (2D) MA$_2$Z$_4$ (M = Ti, Zr, Hf, Nb, Ta; A = Si, Ge; Z = N, P) compounds exhibit both cold metallic and semiconducting behavior. In this work, we present a computational study of lateral heterojunction tunnel diodes based on 2D NbSi$_2$N$_4$ and HfSi$_2$N$_4$ compounds. Employing density functional theory combined with a nonequilibrium Green function method, we investigate the current-voltage ($I$-$V$) characteristics of lateral tunnel diodes with varying barrier thicknesses in both zigzag and armchair orientations. We find that tunnel diodes in the zigzag orientation exhibit significantly higher peak current densities, while those in the armchair orientation display larger peak-to-valley current ratios (PVCRs) compared to the zigzag orientation. Our findings suggest that MA$_2$Z$_4$ materials are promising candidates for realizing NDR tunnel diodes with high PVCR values, which could have potential applications in memory, logic circuits, and other electronic devices.
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