Ε‐Ga2O3: An Emerging Wide Bandgap Piezoelectric Semiconductor for Application in Radio Frequency Resonators. Issue 32 (25th September 2022)

• Record Type: Journal Article
• Authors: Chen, Zimin; Lu, Xing; Tu, Yujia; Chen, Weiqu; Zhang, Zhipeng; Cheng, Shengliang; Chen, Shujian; Luo, Hongtai; He, Zhiyuan; Pei, Yanli; Wang, Gang
• Is Part Of: Advanced science. Volume 9:Issue 32(2022)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2022-09-25
• Subjects: gallium oxide -- piezoelectricity -- radio frequency resonator -- surface acoustic waves; Science -- Periodicals; 505
• DOI: 10.1002/advs.202203927
• Languages: English
• ISSNs: 2198-3844

Abstract

Abstract: The explosion of mobile data from the internet of things (IoT) is leading to the emergence of 5G technology with dramatic frequency band expansion and efficient band allocations. Along with this, the demand for high‐performance filters for 5G radio frequency (RF) front‐ends keeps growing. The most popular 5G filters are constructed by piezoelectric resonators based on AlN semiconductor. However, AlN possesses a piezoelectric constant d 33 lower than 5 pm V −1 and it becomes necessary to develop novel semiconductors with larger piezoelectric constant. In this work, it is shown that strong piezoelectricity exists in ε ‐Ga2 O3 . High‐quality phase‐pure ε ‐Ga2 O3 thin films with a relatively low residual stress are prepared. A switching spectroscopy piezoelectric force microscope (SS‐PFM) measurement is carried out and the piezoelectric constant d 33 of ε ‐Ga2 O3 is determined to be ≈10.8–11.2 pm V −1, which is twice as large as that of AlN. For the first time, surface acoustic wave (SAW) resonators are demonstrated on the ε ‐Ga2 O3 thin films and different vibration modes resonating in the GHz range are observed. The results suggest that ε ‐Ga2 O3 is a great material candidate for application in piezoelectric devices, thanks to its wide bandgap, strong piezoelectric property, small acoustic impedance, and low residual stress. Abstract : The piezoelectricity in ε ‐Ga2 O3 is demonstrated. The piezoelectric coefficient d 33 of ε ‐Ga2 O3 (≈10.8–11.2 pm V –1 ) is twice larger than that of AlN. For the first time, ε ‐Ga2 O3 ‐based surface acoustic wave (SAW) radio‐frequency resonators are demonstrated. The wide bandgap and high piezoelectricity make ε ‐Ga2 O3 a strong competitor to traditional piezoelectric semiconductors in the communication industry.