Scalable Nanofabrication of Two-Dimensional Semiconductor Heterojunction Devices

具有可定制的电学和光电特性的半导体异质结是制造应用于高频电子学、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的新一代电子器件的关键。尽管在不同的研究水平上已经取得了一些进展，但仍然缺乏一种通用的策略来在大规模晶片规模上制备具有良好定义的纳米级结的半导体异质结，这阻碍了它们的广泛商业应用。最近发现的二维过渡金属二卤化物半导体在这方面很有希望，因为它们固有的小尺寸和层状结构，加上容易生长的材料。该奖项旨在通过合理集成多种不同组件和功能的二维材料，以接近原子厚度的方式，实现各种半导体异质结器件的可扩展和高性价比的纳米制造。因此，该奖项通过提供一种新形式的半导体和制造战略来推动纳米电子行业和社区的发展，加快高性能信息存储和逻辑设备的开发，这些设备的运行速度更快，消耗的能量比当前技术更少。该奖项还为研究生和本科生提供多学科培训机会，包括物理学、化学、材料科学、电气工程和纳米技术领域的少数群体和代表性不足的群体。该奖项的结果将用于课程开发。开发了教育模块，以推广到当地的初高中和社区。该研究项目探索了可行的策略，以制备具有所需尺寸、几何结构、组成和定制带偏移的多个异质集成的二维半导体过渡金属二卤化物，所有这些都是高质量纳米级异质结所必需的。形貌可控的二维材料是通过化学气相沉积、低温物理气相沉积和原子层沉积等各种沉积工艺生长出来的，这确保了纳米异质结具有均匀的电学性质、晶片级的可扩展性和原子级的可控性。通过原位/非原位电子显微镜和电子传输测量，研究了材料生长参数对纳米结构变化的影响。一旦确定了优化的生长条件和基本的结构-性质关系，就可以通过将一层二维材料生长在另一层上来制造各种异质结电子器件，包括p-n结、双异质结和超晶格。器件制造采用了一系列用于接触的金属沉积和化学层或原子层沉积，并伴随着标度光学光刻工艺。对异质结器件的载流子输运和电学性能进行了评估，并用透射电子显微镜对其结构特征进行了验证。

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.