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

本项目旨在介绍一种新的电声器件系列，该器件利用半导体衬底中电子和声子之间的耦合来放大微尺度压电硅声腔/谐振器中的体声波。声学谐振器广泛应用于各种应用，包括无线收发器和小型化传感器，在可预见的未来，它们在促进技术创新方面的重要性只会越来越大。几十年来，在压电衬底和石英基谐振器上制造的表面声波（SAW）器件主导了这一领域。在过去的十年中，基于溅射薄膜氮化铝制造的体声波（BAW）器件改变了现状，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段。该提案如果成功，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，同时提供改进的整体性能。首席研究员（PI）在促进多样性方面有着良好的记录，特别是通过支持女学生参与研究，并与全校范围内致力于促进少数族裔研究经验的项目合作。他也是美国国家科学基金会支持的教师研究经验（RET）网站的共同负责人。该项目提供的资源将通过提供新的研究/教学机会，直接影响PI参与所有这些活动。该项目的目标是证明由薄复合压电硅衬底（如铌酸锂（LN）硅）制成的体模谐振腔可以成为一系列设备的滋生地，在这些设备中，通过施加直流电流放大体声波，从而消除了为实现低信号损耗而需要的大驱动区域。该模型和初步结果预测，在GHz频率范围内，在0.2 mm长的硅上硅硅腔中可以实现50 dB的信号增益。可实现增益的大小受限于压电材料的耦合效率和半导体（即硅）中的电子迁移率，这可以在所提出的复合结构中独立优化。为了研究这一新概念并探索其性能极限，计划开展以下具体工作：1)详细研究复合材料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)器件将设计和制造为两个特定的应用；首先是GHz频率的无电路振荡器，其中声电放大补偿了总声腔损失，以实现持续的自发振荡；其次，具有接近零插入损耗的大块模式单片滤波器。3)探索无电路信号放大技术在无源无线压电谐振传感器中的应用，以改善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，比目前无线收发器中使用的现有BAW/SAW滤波器的尺寸小得多。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。

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.