Gigahertz Low-Loss and High Power Handling Acoustic Delay Lines Using Thin-Film Lithium-Niobate-on-Sapphire

Abstract

In this work, we present the first group of gigahertz low-loss, wideband, and high power handling delay lines (ADLs) using a thin-film lithium niobate (LiNbO 3 )-on-sapphire platform. The ADLs leverage a single-phase unidirectional transducer (SPUDT) to efficiently excite the shear horizontal surface acoustic wave (SH-SAW) in the film stack. The fabricated miniature SH-SAW ADL at 1.1 GHz shows a low insertion loss (IL) of 2.8 dB, a wide fractional bandwidth (FBW) of 6.14%, and a fast phase velocity of 5127 m/s. The device also features a high 1-dB compression point (P1dB) of 30.4 dBm. The temperature coefficient of frequency is −45 ppm/K. ADLs with delays between 12 and 172 ns have been implemented, with IL between 2.8 and 8.3 dB. SH-SAW propagation characteristics are extracted, showing a group velocity of 4747 m/s and a propagation loss of 6.73 dB/mm or 31.9 dB/µs. The simultaneous low-loss and high power handling illustrate the great potential of LiNbO 3 -on-sapphire for RF and cross domain applications at gigahertz.

Acoustic wave amplification with thin film silicon bonded on lithium niobate

“…This work demonstrates layer transfer of SOI, though other semiconductors with similar substrate characteristics may also be considered. The approach here is also demonstrated on bulk lithium niobate substrates, but would be equally applicable to substrates with thin film lithium niobate on sapphire or silicon carbide, as have been demonstrated recently for higher electromechanical coupling and enhanced power handling capabilities [46,47]. Device performances may also be enhanced through the application of pulsed electric fields to extend the range of the applied electric field free from thermal effects, and a better understanding of the charge trapping behavior in the interface region.…”

RF acoustic microsystems based on suspended lithium niobate thin films: advances and outlook

“…Another example is the high power handling ADL using solidly mounted thin-film LiNbO 3 . Such devices require engineering the carrier substrate to confine the acoustic waves in the piezoelectric layer [67,73,129]. ADLs in LiNbO 3 on sapphire platforms have shown high P1dB over 30 dBm.…”

“…It allows the integration between LiNbO 3 and various substrates with superior acoustic properties (e.g. silicon carbide [66], sapphire [67], and multi-layer film stack [68][69][70][71][72][73]) or easier to microfabricate (e.g. silicon [74]), as long as the interface is bondingcompatible.…”

Phononic crystals for Love waves based on thin-film lithium niobate

“…the majority of existing SAW devices being based on the former. However, the development of multilayer piezoelectric composite substrates (e.g., smart cut™ piezo on insulator) has facilitated the realization of high-performance SAW devices based on Love waves, which have garnered significant attention due to their advantages [7][8][9]. Compared to Rayleigh waves, Love waves on the surface of the composite substrate can achieve a larger electromechanical coupling coefficient, which is beneficial for ultra-large bandwidth filters.…”

“…This is due to its exceptional piezoelectric properties, high mechanical quality factor, and good chemical stability. Recent developments in thin-film LN materials have made it possible to create a range of Love wave devices, based on composite substrates such as LN-on-SiC [8,9] and LN-on-sapphire [7]. In this paper, we examine in detail the Love wave phononic crystal based on the thin-film LN, using a LN-on-SiC substrate as a demonstration.…”