Single crystal AlGaN bulk acoustic wave resonators on silicon substrates with high electromechanical coupling

Abstract

Bulk acoustic wave (BAW) resonators using single crystal AlGaN piezoelectric films are reported. Metal-organic chemical vapor deposition (MOCVD) growth was used to obtain single crystal AlGaN films on 150-mm diameter <111> silicon substrates with (0002) XRD rocking curve FWHM of 0.37°. Series-configured 12 Ω BAW resonators with resonant frequency of 2.302GHz were fabricated with insertion loss of 0.29dB and an electromechanical coupling of 4.44%. Maximum resonator Q <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">max</inf> was 1277, leading to a figure of merit (FOM) of 57. Unloaded acoustic Q <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">r</inf> was 4243, leading to a FOM of 188. These FOM are the highest reported to date for MOCVD-based single crystal resonators.