Si/SiGe场效应堆叠中在毫开尔文温度下出现的无序特征
Disorder signatures emerging at millikelvin temperatures in Si/SiGe field-effect stacks
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中文总结 AI 辅助
本研究探究Si/SiGe场效应堆叠中毫开尔文温度下的无序特征，发现1.5K磁输运会低估该温度下的无序差异，提出毫开尔文磁输运可优化相关堆叠以提升自旋量子比特性能。
中文摘要 AI 辅助
基于未掺杂Si/SiGe场效应堆叠中栅极定义量子点的电子自旋量子比特，其性能与可扩展性仍受限于栅极堆叠产生的无序。增加Si量子阱深度可降低该无序与量子阱的耦合，而静电电荷历史（例如界面陷阱填充）可进一步改变有效无序分布。尽管这类无序通常通过磁输运和霍尔棒器件的迁移率测量来表征，但针对量子点工作相关的毫开尔文温度下的专门研究仍有限。本研究采用霍尔棒形场效应晶体管的温度依赖磁输运，探究从1.5K到毫开尔文区域内，基于迁移率的无序特征如何依赖量子阱深度与电荷历史。结果表明，1.5K下的磁输运表征可捕捉到与介电界面耦合降低相关的主要迁移率提升，但会低估毫开尔文温度下（尤其低密度区域）出现的无序差异。因此，本研究结果强调，霍尔棒器件的毫开尔文磁输运表征可为优化Si/SiGe场效应堆叠（尤其针对栅极定义量子点自旋量子比特）提供额外见解。
英文摘要
The performance and scalability of electron spin qubits based on gate-defined quantum-dots in undoped Si/SiGe field-effect stacks remain constrained by disorder originating from the gate stack. Its coupling to the quantum well can be reduced by increasing the Si quantum well depth, while electrostatic charge history, for example through interface-trap filling, can further modify the effective disorder landscape. Although such disorder is commonly benchmarked through mobility measurements using magnetotransport and Hall bar devices, dedicated investigations at millikelvin temperatures relevant for quantum-dot operation remain limited. Here, we use temperature-dependent magnetotransport on Hall bar shaped field-effect transistors to investigate how mobility-based disorder signatures depend on quantum-well depth and charge history from \(1.5~\mathrm{K}\) down to the millikelvin regime. We show that magnetotransport characterization at \(1.5~\mathrm{K}\) captures the dominant mobility improvement associated with reduced dielectric-interface coupling, but can underestimate disorder differences that emerge at millikelvin temperatures, particularly in the low-density regime. Our results therefore highlight that millikelvin magnetotransport characterization of Hall bar devices can provide additional insight for optimizing Si/SiGe field-effect stacks, particularly in the context of gate-defined quantum dot spin qubits.
