Piezoelectric AlN films possess high bulk acoustic wave velocity, low acoustic attenuation, and good temperature characteristics. However, AlN film bulk acoustic wave resonators (FBARs) have a relatively small electromechanical coupling coefficient k _eff ². It was recently reported that Cr doping in AlN films increased the piezoelectric constant d ₃₃. The k _t ² of AlN FBARs may thus be enhanced by Cr doping. In this study, we investigated the effect of Cr doping in (0001)-oriented AlN films on k _t ² from the frequency characteristics of high overtone bulk acoustic wave resonators. k _t ² of the Cr-doped AlN films was increased for Cr contents of less than 3%. The maximum k _t ² observed for the Cr_0.012Al_0.088N film was 5.9%, which was approximately 1.4 times higher than that of pure AlN film (k _t ²=4.4%).

压电AlN薄膜具有高体声波速度、低声衰减和良好的温度特性。然而，AlN 薄膜体声波谐振器 (FBAR) 具有相对较小的机电耦合系数k _eff ²。最近有报道称，AlN 薄膜中的 Cr 掺杂增加了压电常数d ₃₃。AlN FBARs的k _t ²因此可以通过Cr掺杂来增强。在本研究中，我们从高泛音体声波谐振器的频率特性研究了 (0001) 取向的 AlN 薄膜中 Cr 掺杂对k _t ²的影响。ķ _吨 ²当 Cr 含量低于 3% 时，Cr 掺杂的 AlN 薄膜的 Cr 含量增加。对于 Cr _0.012 Al _0.088 N 膜观察到的最大k _t ²为5.9%，大约是纯 AlN 膜的 1.4 倍（k _t ² =4.4%）。