Acoustoelectric Amplification in Composite Piezoelectric-Silicon Cavities: A Circuit-Less Amplification Paradigm for RF Signal Processing and Wireless Sensing

该项目旨在引入一种新的电声器件家族，其利用半导体衬底中的电子和声子之间的耦合来放大微尺度硅上压电声学腔/谐振器中的体声波。 声学谐振器用于各种各样的应用，包括无线收发器和微型传感器，它们在促进技术创新方面的重要性在可预见的未来只会增长。几十年来，表面声波（SAW）器件制造的压电基板和石英基谐振器占主导地位的这一领域。在过去的十年中，基于溅射薄膜氮化铝制造的体声波（BAW）器件通过以更小的占地面积和更低的制造成本将声学器件的应用扩展到更高的频带而改变了景观。如果成功，该提案将对进一步扩展BAW谐振器在新领域的应用产生相当大的影响，因为所提出的声电放大将在成本、尺寸和功耗方面提供无与伦比的整体系统级降低，同时提供更好的整体性能。首席研究员（PI）有促进多样性的记录，特别是通过支持女学生从事研究，并与致力于促进少数民族研究经验的大学计划合作。他还是NSF支持的教师研究经验（RET）网站的共同PI。本项目的目的是展示由薄复合压电-硅基片（如锂-硅基复合材料）制成的体模谐振腔，硅可以是一系列器件的滋生地，在这些器件中，体声波通过施加DC电流而被放大，消除了对大的激励区域的需要以实现低的信号损失。模型和初步结果预测，50 dB的信号增益是在0.2毫米长的硅上LN腔在GHz的频率范围内实现。可实现的增益的大小受限于压电材料的耦合效率和半导体中的电子迁移率（即，硅），其可以在所提出的复合结构中独立地优化。为了研究这一新概念并探索性能极限，计划进行以下具体任务：1）详细研究复合结构中声电放大的基本理论，并制定优化增益和功率效率的设计准则。2)设备将被设计和制造为两个特定的应用;第一，电路在GHz频率的振荡器，其中的声电放大补偿总声腔损耗，以实现持续的自发振荡;和第二，体模单片滤波器与近零插入损耗。3)无源无线压电谐振传感器中也将探索无电路信号放大的应用，以提高其有限的分辨率和范围。无电路信号放大如果成功演示，将推动滤波器的发展，以实现可比的信噪比，与现有的BAW/SAW滤波器中使用的无线收发器今天更小的尺寸。这一奖项反映了NSF的法定使命，并已被认为是值得通过评估使用基金会的智力价值和更广泛的影响审查标准的支持。

This project aims to introduce a new family of electro-acoustic devices that utilize the coupling between the electrons and phonons in a semiconducting substrate to amplify bulk acoustic waves in a micro-scale piezoelectric-on-silicon acoustic cavity/resonator. Acoustic resonators are used in a wide variety of applications including wireless transceivers and miniaturized sensors, and their significance in facilitating technological innovation is only going to grow for the foreseeable future. For many decades, surface acoustic wave (SAW) devices fabricated on piezoelectric substrates and quartz-based resonators dominated this field. During the past decade, bulk acoustic wave (BAW) devices fabricated based on sputtered thin-film Aluminum Nitride have changed the landscape by extending the application of acoustic devices to higher frequency bands at smaller footprint and lower manufacturing cost. This proposal, if successful, will have a sizable impact on further extending the application of BAW resonators in new fields as the proposed acoustoelectric amplification will offer unmatched overall system-level reduction in cost, size, and power consumption while offering improved overall performance. The principal investigator (PI) has a track record of promoting diversity, particularly through supporting female students to engage in research and working with university-wide programs that are dedicated to promoting research experience for minorities. He is also a co-PI on an NSF-supported research experience for teachers (RET) site. The resources available through this project will directly impact the PI's involvement in all such activities by providing new research/teaching opportunities.The objective of this project is to demonstrate that bulk-mode resonant cavities made of thin composite piezoelectric-silicon substrates such as lithium-niobate (LN)-on-silicon can be a breeding ground for a flurry of devices in which bulk acoustic waves are amplified through application of a DC current, eliminating the need for large actuation areas to achieve low signal loss. The models and preliminary results predict that 50 dB of signal gain is achievable in a 0.2-mm-long LN-on-silicon cavity at GHz frequency range. The magnitude of the achievable gain is limited to the coupling efficiency of the piezoelectric material and the electron mobility in the semiconductor (i.e., silicon) which could be independently optimized in the proposed composite structure. To study this novel concept and explore the performance limit, the following specific tasks are planned: 1) The underlying theory of acoustoelectric amplification in composite structures will be studied in detail, and the design guidelines for optimized gain and power efficiency will be developed. 2) Devices will be designed and fabricated for two specific applications; first, circuit-less oscillators at GHz frequency in which the acoustoelectric amplification compensates for the total acoustic cavity loss in order to achieve sustained spontaneous oscillation; and second, bulk-mode monolithic filters with near-zero insertion loss. 3) Application of circuit-less signal amplification will also be explored in passive wireless piezoelectric resonant sensors to improve their limited resolution and range. The circuit-less signal amplification, if successfully demonstrated, will advance the development of filters to achieve comparable signal-to-noise ratios with much smaller size than existing BAW/SAW filters used in wireless transceivers today.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.