A Tunable Surface Acoustic Wave Device on Zinc Oxide via acoustoelectric interaction with AIGaN/GaN 2DEG

Surface acoustic wave devices have many applications in signal processing, radio frequency (RF) communications, and sensing [1]. The most common utilization of these devices is for filtering electromagnetic signals in communications systems. However, since the physical dimensions of the inter-digitated transducers (IDT) determine the frequency response, it is very difficult to attain tunable devices for programmable applications. Great effort has been made to achieve an integrated solution to this in III-V semiconductors. One such work utilizes the piezoelectric the GaN buffer layer in an AlGaN/GaN epi for acoustic propagation, while a metal-insulator-semiconductor (MIS) structure is used to tune the SAW response [2]. Unfortunately, the MIS structure results in a weak interaction only achieving a phase tunability of 0.07%. Recent work, uses thin film Zinc Oxide (ZnO) as a piezoelectric on top of n-type ZnO on GaN achieving a high tunability of. 9% [3]. In this work, we demonstrate a ZnO on AIGaN/GaN heterostructure capable of achieving high tunability as well as impacting properties of the SAW filter not previously reported.