Scalable Nanofabrication of Two-Dimensional Semiconductor Heterojunction Devices

具有定制电子和光电特性的半导体异质结构是制造新一代电子器件的关键，用于高频电子，传感器，探测器，太赫兹源，低功率隧道场效应晶体管和计算存储器。尽管在不同的研究水平上取得了一些进展，但在大晶圆尺度上制造具有良好定义的纳米级结的半导体异质结构的通用策略仍然缺乏，阻碍了其广泛的商业应用。最近发现的二维过渡金属二硫族半导体由于其固有的小尺寸和层状结构以及易于材料生长而在这方面很有前途。该奖项旨在通过合理集成具有不同组件和功能的近原子厚度的多种二维材料，研究各种半导体异质结器件的可扩展性和成本效益纳米制造。因此，该奖项通过提供一种新型半导体和制造战略，加速高性能信息存储和逻辑设备的开发，从而推动纳米电子工业和社区的发展，这些设备比现有技术运行速度更快，能耗更低。该奖项还为研究生和本科生提供多学科培训机会，包括物理、化学、材料科学、电子工程和纳米技术领域的少数族裔和未被充分代表的群体。该奖项的成果将用于课程开发。开发教育模块是为了向当地的初中、高中和社区推广。本研究项目探索可行的策略，以制造具有理想尺寸、几何形状、成分和定制带偏移的非均质集成多二维半导体过渡金属二硫族化合物，这些都是高质量纳米级异质结所必需的。形貌控制的二维材料通过化学气相沉积、低温物理气相沉积和原子层沉积等多种沉积工艺生长，确保了纳米异质结的均匀电性能、晶圆级可扩展性和原子级控制。通过原位/非原位透射电镜和电子输运测量评估了材料生长参数对纳米级结构变化的影响。一旦优化的生长条件和潜在的结构-性能关系建立，通过在另一层上生长一层二维材料来制造各种异质结电子器件，包括pn结，双异质结和超晶格。该器件的制造采用了一系列的金属沉积触点和化学或原子层沉积，伴随着可扩展的光学光刻工艺。对异质结器件的载流子输运和电学性能进行了评价，并与透射电子显微镜的结构表征相印证。

Semiconductor heterostructures with tailored electronic and optoelectronic properties are a key in fabricating new generation of electronic devices for applications in high-frequency electronics, sensors, detectors, terahertz sources, low power tunnel field effect transistors, and computing memories. Despite some progress being made at different research levels, a versatile strategy to fabricate semiconductor heterostructures with well-defined nanoscale junctions on a large wafer-scale is still lacking, impeding their widespread commercial applications. Recently discovered two-dimensional transition metal dichalcogenide semiconductors are promising in this respect owing to their intrinsically small sizes and layered structures coupled with facile material growth. This award investigates the scalable and cost-effective nanofabrication of various semiconductor heterojunction devices by rationally integrating multiple two-dimensional materials of dissimilar components and functionalities with near atom thickness. Accordingly, the award advances nano-electronics industries and communities by delivering a new form of semiconductors and manufacturing strategies, expediting the development of high-performance information storage and logic devices that operate at higher speed and dissipate less energy than current technologies. The award also offers multidisciplinary training opportunities for graduate and undergraduate students including minority and underrepresented groups in physics, chemistry, materials science, electrical engineering, and nanotechnology. The outcomes from the award are implemented for curriculum development. Educational modules are developed for outreach to local mid and high schools and communities. This research project explores viable stratgies to fabricate heterogenously-integrated multiple two-dimensional semiconducting transition metal dichalcogenides with desired dimensions, geometries, compositions and tailored band-offset, all essential for high-quality nanoscale heterojunctions. Morphology controlled two-dimensional materials are grown by various deposition processes including chemical vapor deposition, low temperature physical vapor deposition, and atomic layer deposition, which ensures uniform electrical properties, wafer-level scalability and atomic-level control in the nanoscale heterojunctions. The effect of material growth parameters on nanoscale structural variations are evaluated by in-situ/ex-situ transmission electron microscopy and electron transport measurements. Once the optimized growth conditions and the underlying structure-property relationships are established, a variety of heterojunction electronic devices are fabricated by growing one layer of the two-dimensional material on top of the other, which includes p-n junction, double heterojunction, and superlattices. The device fabrication employs a series of metal depositions for contacts and chemical or atomic layer depositions, accompanied by a scalalabe optical lithography process. Carrier transport and the electrical performances of the heterojunction devices are evaluated and are corroborated with the structural characterizations by transmission electron microscopy.