Low loss surface acoustic wave SAW devices based on Al1-xMxN (M=Cr, Y, Sc) thin films

Abstract

In this work, the coupling-of-modes (COM) approach and P-matrix model are used to investigate the frequency response of a two-port surface acoustic wave SAW delay line based on piezoelectric AlN doped with transition metals. The elastic and piezoelectric properties of Al1-xMxN (M = Cr, Y, Sc) thin films are theoretically investigated using the density functional theory (DFT). The results revealed that doping with Cr at x = 25% increases the piezoelectric response up to 288% compared to pure AlN, which is better than results obtained by others transition metal (Sc, Y) dopants. The frequency response of a two-port SAW delay line IDT/Al1-xMxN (M = Cr, Y, Sc)/Si shows that increasing dopants (Cr, Y and Sc) concentration considerably enhances the insertion loss and causes a significant shift down in the operating frequency. The obtained results are helpful in the design and fabrication of acoustic sensors and resonators with improved performances.