Enhanced conductance at interfaces by ballistic thermal injection

在半导体电子产品中，阻碍理想工作效率和性能的主要瓶颈之一是无法有效地减缓温度上升。这些器件中异质界面处的热阻是这些有害温升的主要来源。这项工作将开发新的实验探针来研究高频电子设备中典型的电子-声子非平衡状态下金属/半导体界面的传热过程。这项工作的动机是假设一个平行途径的热传导跨越界面是可能的，通过电子将超过声子界面传导单独。这项工作的结果将为金属/掺杂半导体和金属/栅氧化物/掺杂半导体界面的设计提供信息，通过弹道热注入最大化电子热传导来增强热传导。该项目将包括几个外展和教育举措，包括每年在夏洛茨维尔社区为K-12设计的当地外展活动，以及本科和研究生水平的课程改进。该项目的目标是利用最近发现的传热机制-弹道热注入-来操纵电子-声子非平衡状态，以增强传统上表现出高声子热阻的半导体界面的散热。该项目将研究驱动电子-声子相互作用的基本传热机制，这是通过开发一种具有波长可调到中红外的新型超快泵浦探测系统实现的。这个项目更广泛的影响在于理解独特的纳米尺度传热机制，这将导致新的界面设计来降低温度，例如：延迟逻辑器件摩尔定律的不祥终结；在热驱动相变存储器中推动更高的存储密度，以跟上Kryder定律的步伐；在WBG和UWBG功率和RF器件中实现本质上可能的功率密度，而不受热失效的限制；并通过独立的电气和热载体工程，最大限度地提高能量转换设备（如光伏、热电、热离子）的效率。这项工作的发现将导致新的界面设计概念，以拥抱这种新的界面传热机制，这将最终导致更有效的技术。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

One of the primary bottlenecks that is inhibiting the ideal operating efficiency and performance in semiconductor-based electronics is the inability to effectively mitigate temperature rises. The thermal resistances at heterogeneous interfaces in these devices are the primary source of these deleterious temperature rises. This work will develop novel experimental probes to study the heat transfer processes across metal/semiconductor interfaces during conditions of electron-phonon nonequilibrium that are typical near interfaces in high frequency electronic devices. This work is motivated by the hypothesis that a parallel pathway for heat conduction across interfaces is possible via electrons that will exceed phononic interfacial conduction alone. The results of this work will inform the design of both metal/doped semiconductor and metal/gate oxide/doped semiconductor interfaces to enhance thermal conduction by maximizing electron thermal conductance via ballistic thermal injection. This project will encompass several outreach and educational initiatives, including a local outreach event in the Charlottesville community annually designed for K-12, and curriculum enhancement at both undergraduate and graduate levels. The goal of this project is to leverage a recently-discovered heat transfer mechanism – ballistic thermal injection – to manipulate conditions of electron-phonon nonequilibrium to enhance heat dissipation across semiconductor-based interfaces that traditionally exhibit high phonon thermal resistances. This project will study the fundamental heat transfer mechanisms that drive the electron-phonon interaction both across and near interfaces, which is enabled by the development of a novel ultrafast pump-probe system with wavelength tunability into the mid-infrared. The broader impacts of this project are in the understanding of unique nanoscale heat transfer mechanisms that will lead to new interface designs to reduce temperature that can, for example: delay the ominous end to Moore’s Law for logic devices; push to higher storge densities in thermally-driven phase change memory to keep pace with Kryder’s Law; achieve the intrinsically possible power densities in WBG and UWBG power and RF devices without being limited by thermal failures; and maximize efficiency of energy conversion devices (e.g., photovoltaic, thermoelectric, thermionic) through independent engineering of electrical and thermal carriers. The findings from this work will result in new interfacial design concepts to embrace this novel mechanism of interfacial heat transfer, which will ultimately lead to more efficient technologies.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.