A Reconfigurable Surface Acoustic Wave Filter on ZnO/AlGaN/GaN Heterostructure

With the increasing number of filters on radio frequency front ends, especially in handheld systems, such as cell phones, there has been a growing interest developing reconfigurable filters to accommodate all of the frequencies used modern communication protocols. This article demonstrates a voltage-tunable filter by utilizing the acoustoelectric effect between acoustic waves on zinc oxide (ZnO) and the 2-D electron gas (2DEG) in the interface of aluminum gallium nitride (AlGaN) and gallium nitride (GaN). The device is capable of tuning the center frequency by up to 0.78%. Furthermore, the emergence of an accumulation region at the ZnO/AlGaN interface allows for control of the sideband rejection ratio by 16 dB and the bandwidth by 12 dB, demonstrating a degree of reconfigurability that is previously not reported.