Use of heavy dielectric materials in solidly mounted A1 mode resonators based on lithium niobate

Abstract

Abstract This paper discusses applicability of dielectric materials with high acoustic impedance a for the use in A1 Lamb mode solidly mounted resonator (SMR) with large eletromechanical coupling factor k2 . The study first shows that the use of metal as reflector creates parasitic capacitance p, which reduces k2 significantly. Then, A1 Lamb mode SMRs are designed using HfN, HfO2, WN, WO3 etc., and achievable performances are compared. When either HfN, HfO2, WN, or WO3 is employed, relative large k2 up to 25% is achievable. For further k2 enhancement, a hybrid reflector configuration is also examined, wherein HfN is applied only to the top high-a layer and W is applied to the others. The result indicates that p caused by the W layers is still significant, and k2 becomes worse in total.