发表机构
Tohoku University; National Institute of Information and Communications Technology（东北大学; 信息通信研究机构）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
本研究开发了侧壁间隔层钝化的外延NbN/AlN/NbN约瑟夫森结，通过简化工艺减少非晶介电材料，实现了高间隙电压和宽范围临界电流密度，为高相干氮化物超导量子比特提供了可扩展制造平台。
AI 中文摘要
外延NbN/AlN/NbN约瑟夫森结因其晶体隧道势垒和NbN的高超导转变温度，被认为是传统Al/AlO$_x$/Al结用于超导量子比特的有前景替代方案。然而，将它们集成到量子电路中通常需要涉及非晶层间介电质的复杂制造工艺，这会降低量子比特的相干时间。为解决这些问题，我们开发了侧壁间隔层钝化的外延NbN/AlN/NbN结，采用了一种减少非晶介电材料体积和制造复杂性的工艺。所制备的结表现出约5.6 mV的大间隙电压和低亚间隙漏电流。通过改变AlN隧道势垒的厚度，在0.3至10$^4$ A/cm$^2$的宽临界电流密度${\it J}_c$范围内制备了高质量结。此外，缓冲氢氟酸处理前后电流-电压特性的比较表明，湿法刻蚀工艺未降低结的电学特性。这些结果建立了一种可扩展的外延约瑟夫森结制造工艺，并为高相干性氮化物基超导量子比特提供了有前景的平台。
英文摘要
Epitaxial NbN/AlN/NbN Josephson junctions are promising alternatives to conventional Al/AlO$_x$/Al junctions for superconducting qubits due to their crystalline tunnel barriers and the high transition temperature of NbN. However, their integration into quantum circuits typically requires complex fabrication processes involving amorphous interlayer dielectrics, which can degrade qubit coherence times. To address these issues, we developed sidewall spacer passivated epitaxial NbN/AlN/NbN junctions using a fabrication process that reduces both the volume of amorphous dielectric material and fabrication complexity. The fabricated junctions exhibited a large gap voltage of approximately 5.6 mV and low subgap leakage currents. By varying the thickness of the AlN tunnel barrier, high-quality junctions were fabricated over a wide range of critical current densities ${\it J}_c$, from 0.3 to 10$^4$ A/cm$^2$. In addition, the comparison of the current-voltage characteristics before and after buffered hydrofluoric acid treatment indicated that the wet etching process did not degrade the electrical characteristics of the junctions. These results establish a scalable fabrication process for epitaxial Josephson junctions and provide a promising platform for high-coherence nitride-based superconducting qubits.
Comments9 pages, 4 figures
