밀리미터파 RF 필터를 위한 육방정계 질화붕소 기반의 표면탄성파 장치

Abstract

Due to a simple structure, low power consumption, and small form-factor, surface acoustic wave (SAW) filters have been widely adopted to the RF front-end in modern communication devices. To select a specific frequency band and increase the communication capacity, the latest Long-Term-Evolution (LTE) mobile devices, for instance, are equipped with more than 30 such filters. For higher speed communications, the radio frequency for mobile devices keeps increasing, and the newest fifth-generation wireless network utilized up to 39 GHz. Here, we show the use of hexagonal boron nitride can overcome the physical limit that the maximum frequency of the conventional SAW filters stays below 3 GHz commercially. Our study using first principles’ analysis shows a LiNbO3/h-BN/SiO2 layered structure of surface acoustic wave filter that can operate at 21 GHz and 46 GHz as fundamental and first higher-order resonance frequencies, respectively, are possible with the interdigital transducer period of 150 nm, which can be fabricated with modern lithography technology. Furthermore, in the first higher-order resonance mode, it achieved a high electromechanical coupling coefficient K2 of 6.8 %. As such, a low-power RF filter for 5G and beyond can be realized with the surface acoustic wave of hexagonal boron nitride.