分子束外延生长的ZnO压电薄膜及其声表面波器件特性

用RF-MBE在蓝宝石(0001)衬底上引入MgO和低温ZnO双缓冲层生长了ZnO薄膜,并制备了声表面波器件。在ZnO薄膜中,仅观测到(0002)面的XRD,且衍射峰增强,半高宽减小,表明ZnO薄膜c轴取向性更好,晶体结构更优。室温下自由激子吸收峰更尖锐和吸收边更陡峭以及仅观测到自由激子发光,且发光线宽变窄、发光强度变大,表明ZnO薄膜缺陷密度减小,薄膜质量提高。测得该ZnO压电薄膜的电阻率高达4×10⁷ Ω·cm,其声表面波的速度高达5 010 m/s。

Surface Acoustic Wave Based on ZnO Thin Films Grown by RF-MBE

High quality ZnO piezoelectric thin films have been grown by RF-MBE on sapphire(0001) substrate with MgO and ZnO double buffer layers.Only ZnO(0002) diffraction peak was observed in the XRD patterns,with a narrow FWHM of 0.10°.A sharp absorption peak and a steep absorption edge were observed in absorption spectra,only one PL peak from free exciton emission,with a narrow FWHM of 12.7 nm,was obtained in PL spectra.The electrical resistivity of the ZnO thin films is up to 4×107 Ω·cm.These results indicate that ZnO thin films have good c-axis orientation with wurtzite structure,low defect densities and low background carrier concentration.This is mainly due to that the MgO and ZnO double buffer layers accommodated the mismatch between the ZnO thin films and the sapphire substrate.The SAW devices based on the high quality ZnO thin films were fabricated.The center frequency of the surface acoustic wave(SAW) filter is 835 MHz,and the SAW propagation speed is up to 5 010 m/s,indicating that the MgO and ZnO double buffer layers not only improved the quality of the ZnO films,but also improved the piezoelectric properties of the films.