Piezoelectric and electroacoustic properties of V-doped and Ta-doped AlN thin films

Abstract

In this paper we analyze the effects of doping AlN films with vanadium and tantalum to concentrations up to 6% atomic. The structure and composition of the new compounds are assessed as a function of the dopant concentration by x-ray diffraction (XRD), IR reflectance and Rutherford backscattering spectrometry (RBS). Test devices consisting on bulk acoustic wave resonators are used to assess the piezoelectric activity of the compounds as well as other material properties, such as the acoustic velocities and the piezoelectric constant. Films doped with vanadium show an overall worsening of their main properties for acoustics applications. Films doped with tantalum show variations in their wurtzite crystal structure that suggests that an improvement of the piezoelectric activity can be achieved as long as films exhibiting good crystal quality and homogeneous dipole orientation can be grown.