Systematical Study of the Basic Properties of Surface Acoustic Wave Devices Based on ZnO and GaN Multilayers

Abstract

Recently, surface acoustic wave (SAW) devices based on layered structures are a popular area of research. Multilayered structures, including ZnO and GaN, have shown great performance and can be applied in diverse fields. Meanwhile, thin films, such as AlGaN and n-ZnO, can be added to these structures to form a 2-D electron gas (2DEG) which makes the devices tunable. This work systematically studies the basic properties of SAW devices based on ZnO and GaN multilayers via COMSOL Multiphysics. The sorts of structures with different crystal orientations are simulated, and various acoustic modes are considered. Results show that a range of phase velocity from about 2700 m/s to 6500 m/s can be achieved, and devices based on ZnO and GaN multilayers can meet the requirements of the electromechanical coupling coefficient from about 0 to 7%. Every structure’s unique properties are valuable for diverse applications. For example, c-ZnO/c-GaN/c-sapphire structure can be used for high-frequency and large-bandwidth SAW devices, while SAW devices based on a-ZnO/a-GaN/r-sapphire and 2DEG are suitable for programmable SAW sensors. This work has great reference value for future research into SAW devices.

ZnO/glass thin film surface acoustic waves for efficient digital acoustofluidics and active surface cleaning

“…The maximum value for Sezawa mode is 1.6% at a normalized thickness of 0.41, which is slightly larger than those reported in the literature (e.g., 0.45 to 0.50 %) [23,24]. For the Sezawa mode, as its frequency is much higher, the wave energy is more confined to the interface and the ZnO thin film, which ultimately leads to a larger coupling coefficient [25][26][27]. It was reported that the k 2 values of Sezawa wave mode are decreased as the wavelength is increased [12].…”

“…When the power applied is increased above 4 W, the water droplet was observed to eject from the surface instead of just moving or sliding on the surface of the SAW device. Figure 4e shows that with a relatively high power of 9.62 W, acoustic energy coupling into the water droplet becomes so large that the water droplet can be deformed into an elongated liquid column and ejected from the surface after 0.558 s [26]. Figure 4f shows the jetting speeds which were calculated as the distances moved by the droplet along the ejected direction in the horizontal plane, divided by the time to experience the whole jetting phenomenon.…”

The effects of etching time and hydrogen peroxide concentration on the ZnO/glass substrate

“…In order for ZnO to be applied in optoelectronic devices, the fabrication of ZnO thin films on the numerous substrates plays a very important role. Examples of applications in the use of ZnO as a semiconductor type are UV light emitters [1], surface acoustic wave devices [2], gas sensing [3], piezoelectric interdigital transducers [4], self-powered UV photodetectors [5], supercapacitors [6], varistors [7], and solar cells [8]. ZnO is also used in cosmetics as an ingredient in creams and lotions, as well as a UV filter in sunscreens.…”