Schuwalow Sergej, Schröter Niels B M, Gukelberger Jan, Thomas Candice, Strocov Vladimir, Gamble John, Chikina Alla, Caputo Marco, Krieger Jonas, Gardner Geoffrey C, Troyer Matthias, Aeppli Gabriel, Manfra Michael J, Krogstrup Peter
Center for Quantum Devices Niels Bohr Institute University of Copenhagen and Microsoft Quantum Materials Lab Copenhagen Lyngby Denmark.
Paul Scherrer Institut Swiss Light Source PSI Villigen CH-5232 Switzerland.
Adv Sci (Weinh). 2020 Dec 31;8(4):2003087. doi: 10.1002/advs.202003087. eCollection 2021 Feb.
The design of epitaxial semiconductor-superconductor and semiconductor-metal quantum devices requires a detailed understanding of the interfacial electronic band structure. However, the band alignment of buried interfaces is difficult to predict theoretically and to measure experimentally. This work presents a procedure that allows to reliably determine critical parameters for engineering quantum devices; band offset, band bending profile, and number of occupied quantum well subbands of interfacial accumulation layers at semiconductor-metal interfaces. Soft X-ray angle-resolved photoemission is used to directly measure the quantum well states as well as valence bands and core levels for the InAs(100)/Al interface, an important platform for Majorana-zero-mode based topological qubits, and demonstrate that the fabrication process strongly influences the band offset, which in turn controls the topological phase diagrams. Since the method is transferable to other narrow gap semiconductors, it can be used more generally for engineering semiconductor-metal and semiconductor-superconductor interfaces in gate-tunable superconducting devices.
外延半导体 - 超导体和半导体 - 金属量子器件的设计需要对界面电子能带结构有详细的了解。然而，掩埋界面的能带排列在理论上难以预测，在实验上也难以测量。这项工作提出了一种程序，能够可靠地确定用于工程量子器件的关键参数；半导体 - 金属界面处的能带偏移、能带弯曲轮廓以及界面积累层中占据的量子阱子带数量。软X射线角分辨光电子能谱用于直接测量InAs(100)/Al界面的量子阱态以及价带和芯能级，该界面是基于马约拉纳零模的拓扑量子比特的重要平台，并证明制造工艺强烈影响能带偏移，而能带偏移又反过来控制拓扑相图。由于该方法可转移到其他窄带隙半导体，它可更广泛地用于工程化栅极可调超导器件中的半导体 - 金属和半导体 - 超导体界面。
