Single-Crystal AlN Wafer-Based Bulk Acoustic Resonators for Piezoelectric Power Conversion

TL;DR

This paper presents the first single-crystal AlN wafer-based bulk acoustic resonator with high quality factor and strong potential for efficient piezoelectric power conversion, demonstrating suppression of spurious modes and promising thermal properties.

Contribution

It introduces a novel AlN-based bulk acoustic resonator with high performance metrics and improved mode suppression, advancing piezoelectric power conversion technology.

Findings

High $Q$ of 1677 achieved

Effective suppression of spurious modes

Competitive $f \, \cdot \, Q$ product

Abstract

In this work, we demonstrate the first single-crystal aluminum nitride (AlN) wafer-based thickness-extensional (TE) mode bulk acoustic resonator for piezoelectric power conversion. The device exhibits a high series resonance 3-dB quality factor ($Q$) of 1677 and an electromechanical coupling coefficient ($k^2$) of 6.1%, highlighting the strong potential of AlN resonators for efficient power conversion. To suppress in-band spurious modes, a grounded ring structure is proposed and experimentally validated. The measured frequency-domain impedance response shows a spurious suppression of the spectrum above the resonance at 13.52 MHz. A comparative analysis with prior PZT, LN, and LT-based resonators indicates that AlN achieves a competitive figure of merit and $f \cdot Q$ product, while its material thermal conductivity is orders of magnitude higher than that of the incumbent piezoelectric power-converter resonators. The power-handling capability is expected to be superior in AlN single-crystal wafers and will be demonstrated in ongoing experiments. These results suggest that AlN offers a promising platform for compact, robust piezoelectric power converters and next-generation power electronic systems.