发表机构
QuTech and Kavli Institute of Nanoscience, Delft University of Technology; Materials Department, University of California, Santa Barbara; Department of Materials, University of Oxford（代尔夫特理工大学量子纳米科学卡弗里研究所和QuTech; 加州大学圣塔芭芭拉分校材料系; 牛津大学材料系）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
本研究通过固态反应在低温下合成超导难熔金属锗化物，用于Ge/SiGe量子器件，发现界面反应受限是主要障碍。
AI 中文摘要
固态相反应为将超导体集成到Ge/SiGe异质结构中提供了一条途径，但在埋藏的Ge量子阱附近形成高质量超导层仍然具有挑战性。我们研究了V、Ta和Nb与元素Ge以及与Ge/SiGe异质结构的Si$_{0.2}$Ge$_{0.8}$势垒在365-390 $^\circ$C加工温度下的反应。截面电子显微镜和低温电输运测量表明，在390 $^\circ$C下沉积于Ge上时，其中约2 nm的金属增量被生长停顿隔开以进行原位退火，在整个沉积膜中产生反应，并分别在约0.14 K（V-Ge）、2.1 K（Ta-Ge）和2.8 K（Nb-Ge）处产生超导转变。Nb-Ge层在2.1 K时的面外临界场约为0.8 T。在异质结构样品中，互混被限制在金属-SiGe界面附近约5-12 nm厚的区域内，留下大量残余金属层。显微镜和输运测量共同表明，该残余膜主导了所测得的超导响应。这些结果确立了低温形成超导难熔金属-Ge层的方法，同时确定了有限的界面反应是将该方法扩展到埋藏量子阱的主要障碍。
英文摘要
Solid-phase reactions offer a route to integrate superconductors into Ge/SiGe heterostructures, but forming high-quality superconducting layers near the buried Ge quantum well remains challenging. We investigate reactions of V, Ta, and Nb with elemental Ge and with the Si$_{0.2}$Ge$_{0.8}$ barrier of Ge/SiGe heterostructures at processing temperatures of 365-390 $^\circ$C. Cross-sectional electron microscopy and low-temperature electrical transport show that deposition on Ge at 390 $^\circ$C, in which approximately 2 nm metal increments are separated by growth stops for in-situ annealing, produces reactions throughout the deposited films and superconducting transitions at approximately 0.14 K for V-Ge, 2.1 K for Ta-Ge, and 2.8 K for Nb-Ge. The Nb-Ge layer has an out-of-plane critical field of approximately 0.8 T at 2.1 K. In the heterostructure samples, intermixing is confined to regions approximately 5-12 nm thick near the metal-SiGe interface, leaving a substantial residual metal layer. Microscopy and transport together suggest that this residual film dominates the measured superconducting response. These results establish low-temperature formation of superconducting refractory-metal-Ge layers while identifying the limited interfacial reaction as the principal obstacle to extending this approach toward the buried quantum well.
