Ramanayaka A N, Tang Ke, Hagmann J A, Kim Hyun-Soo, Simons D S, Richter C A, Pomeroy J M
National Institute of Standards & Technology, Gaithersburg, Maryland 20899, USA.
Joint Quantum Institute, University of Maryland, College Park, Maryland 20742, USA.
AIP Adv. 2019;9(12). doi: 10.1063/1.5128098.
Across solid state quantum information, materials deficiencies limit performance through enhanced relaxation, charge defect motion or isotopic spin noise. While classical measurements of device performance provide cursory guidance, specific qualifying metrics and measurements applicable to quantum devices are needed. For quantum applications, new materials metrics, e.g., enrichment, are needed, while existing, classical metrics like mobility might be relaxed compared to conventional electronics. In this work, we examine locally grown silicon superior in enrichment, but inferior in chemical purity compared to commercial-silicon, as part of an effort to underpin the materials standards needed for quantum grade silicon and establish a standard approach for intercomparison of these materials. We use a custom, mass-selected ion beam deposition technique, which has produced isotopic enrichment levels up to 99.99998 % Si, to isotopically enrich Si, but with chemical purity > 99.97% due the MBE techniques used. From this epitaxial silicon, we fabricate top-gated Hall bar devices simultaneously on the Si and on the adjacent natural abundance Si substrate for intercomparison. Using standard-methods, we measure maximum mobilities of at an electron density of cm and at an electron density of cm at K for devices fabricated on Si and Si, respectively. For magnetic fields T, both devices demonstrate well developed Shubnikov-de Haas (SdH) oscillations in the longitudinal magnetoresistance. This provides transport characteristics of isotopically enriched Si, and will serve as a benchmark for classical transport of Si at its current state, and low temperature, epitaxially grown Si for quantum devices more generally.
在固态量子信息领域，材料缺陷会通过增强弛豫、电荷缺陷运动或同位素自旋噪声来限制性能。虽然对器件性能的经典测量能提供粗略的指导，但仍需要适用于量子器件的特定合格指标和测量方法。对于量子应用，需要新的材料指标，例如富集度，而与传统电子学相比，诸如迁移率等现有的经典指标可能会放宽要求。在这项工作中，我们研究了局部生长的硅，其富集度优于商用硅，但化学纯度低于商用硅，这是为了确定量子级硅所需的材料标准并建立这些材料相互比较的标准方法所做努力的一部分。我们使用一种定制的、质量选择离子束沉积技术对硅进行同位素富集，该技术已产生高达99.99998%的硅同位素富集水平，但由于使用了分子束外延技术，化学纯度>99.97%。从这种外延硅中，我们在硅和相邻的天然丰度硅衬底上同时制造顶栅霍尔条形器件以进行相互比较。使用标准方法，我们分别测量了在硅和天然丰度硅上制造的器件在电子密度为 cm 时，于 K 下的最大迁移率为 以及在电子密度为 cm 时的最大迁移率为 。对于磁场 T，两个器件在纵向磁阻中均表现出良好的舒布尼科夫 - 德哈斯（SdH）振荡。这提供了同位素富集硅的输运特性，并将作为当前状态下硅的经典输运以及更普遍的用于量子器件的低温外延生长硅的基准。
