In this dissertation, heterostructured micro-acoustic devices are explored that leverage the interactions between acoustic phonons and electrons to enable radio frequency (RF) signal amplification or attenuation. Thin films of piezoelectric and semiconductor material are tailored into a heterostructure that allows for a strong acoustoelectric (AE) effect due to the combination of high electromechanical coupling and high electron drift velocity in said films respectively. In such devices, the relative electron drift and acoustic velocities could determine whether the RF signal undergoes AE gain or loss, rendering the device non-reciprocal. This is a highly sought-after property for building isolators and circulators which facilitate full-duplex communication and interference cancellation in forthcoming generations of telecommunication. The AE effect attracted a great deal of attention during the mid-twentieth century, ultimately leading to the invention of interdigital transducers for excitation of surface acoustic waves as the preferred enabler of such effect which is still being investigated. However, the widespread application of such class of AE components is hindered by their poor performance metrics such as low power efficiency and limited frequency scaling. In this dissertation, by taking advantage of the superior properties of Lamb waves, namely, higher frequency scaling and lower insertion loss at larger available bandwidth, power-efficient and high power-handling AE devices are realized in a lithium niobate on silicon micromachined platform. Through this platform in this work, at few milliwatts of bias power, more than 30 dB of AE gain with larger than 40 dB nonreciprocal transmission is realized in a sub-millimeter form factor. This novel platform enables single-chip realization of frequency-disperse high power-handling ultrasonic signal processors with numerous functionalities such as gain, non-reciprocal behavior, tunable attenuation, insertion delay, and switching. This could significantly reduce the number of components in an RF frontend module, shrink their footprints, and facilitate packaging.
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Doctor of Philosophy (Ph.D.)
College of Engineering and Computer Science
Electrical and Computer Engineering
Length of Campus-only Access
Doctoral Dissertation (Open Access)
Mansoorzare, Hakhamanesh, "Acoustoelectric Amplification in Piezoelectric-Silicon Micromachined Lamb Wave Devices" (2021). Electronic Theses and Dissertations, 2020-. 900.