Acoustic wave device having stacked piezoelectric layers between electrodes
Aspects of this disclosure relate to acoustic wave devices that include a plurality of stacked piezoelectric layers positioned between electrodes. Such acoustic wave devices can excite an overtone mode as a main mode. Related acoustic wave filters, radio frequency modules, wireless communication devices, and methods are also disclosed.
1 . An acoustic wave device with multiple piezoelectric layers, the acoustic wave device comprising:
a first electrode;
a second electrode; and
a plurality of piezoelectric layers stacked with each other and positioned between the first electrode and the second electrode, the plurality of piezoelectric layers including a first piezoelectric layer and a second piezoelectric layer, the first piezoelectric layer having a first c-axis and the second piezoelectric layer having a second c-axis, the first c-axis being oriented in a different direction than the second c-axis, the plurality of piezoelectric layers together with the first and second electrodes configured to excite an overtone mode as a main mode of the acoustic wave device, and a resonant frequency of the overtone mode is in a range from 5 gigahertz to 12 gigahertz.
2 . The acoustic wave device of claim 1 wherein the overtone mode is a second overtone mode.
3 . The acoustic wave device of claim 1 wherein the first piezoelectric layer and the second piezoelectric layer are in physical contact with each other in a main acoustically active region of the acoustic wave device.
4 . The acoustic wave device of claim 1 wherein the first piezoelectric layer and the second piezoelectric layer both include a same piezoelectric material.
5 . The acoustic wave device of claim 1 wherein the first c-axis is oriented in a substantially opposite direction than the second c-axis.
6 . The acoustic wave device of claim 1 wherein the first piezoelectric layer has a different doping concentration than the second piezoelectric layer.
7 . The acoustic wave device of claim 1 wherein the plurality of piezoelectric layers includes a third piezoelectric layer, the second piezoelectric layer is positioned between the first piezoelectric layer and the third piezoelectric layer, and the third piezoelectric layer has a c-axis oriented in substantially a same direction as the c-axis of the first piezoelectric layer.
8 . The acoustic wave device of claim 1 wherein the plurality of piezoelectric layers have a combined thickness in a range from 0.2 micrometer to 5 micrometers.
9 . The acoustic wave device of claim 8 wherein the first and second piezoelectric layers each include aluminum nitride.
10 . The acoustic wave device of claim 9 wherein the first and second piezoelectric layers are each doped with a dopant.
11 . The acoustic wave device of claim 1 wherein the acoustic wave device is a film bulk acoustic wave resonator.
12 . The acoustic wave device of claim 1 wherein the acoustic wave device is a Lamb wave resonator.
13 . The acoustic wave device of claim 1 wherein the first electrode and the second electrode are the only electrodes of the acoustic wave device.
14 . A radio frequency module comprising:
an acoustic wave filter that includes the acoustic wave device of claim 1 ; and
a radio frequency circuit element coupled to the acoustic wave filter, the acoustic wave filter and the radio frequency circuit element being enclosed within a common package.
15 . An acoustic wave device with multiple piezoelectric layers, the acoustic wave device comprising:
a first electrode;
a second electrode, the first electrode and the second electrode being the only electrodes of the acoustic wave device; and
a plurality of piezoelectric layers stacked with each other and positioned between the first electrode and the second electrode, the plurality of piezoelectric layers including a first piezoelectric layer and a second piezoelectric layer, the plurality of piezoelectric layers together with the first and second electrodes configured to excite an overtone mode as a main mode of the acoustic wave device, and a resonant frequency of the overtone mode is in a range from 5 gigahertz to 12 gigahertz.
16 . An acoustic wave filter comprising:
an acoustic wave device that includes a first electrode, a second electrode, and a plurality of piezoelectric layers stacked with each other and positioned between the first electrode and the second electrode, the first electrode and the second electrode being the only electrodes of the acoustic wave device, the plurality of piezoelectric layers including a first piezoelectric layer and a second piezoelectric layer, the acoustic wave device configured to excite an overtone mode as a main mode, and a resonant frequency of the overtone mode is in a range from 5 gigahertz to 12 gigahertz; and
a plurality of additional acoustic wave devices, the acoustic wave device and the plurality of additional acoustic wave devices together configured to filter a radio frequency signal.
17 . The acoustic wave filter of claim 16 wherein the acoustic wave device is configured to suppress a nonlinearity of the acoustic wave filter.
18 . The acoustic wave filter of claim 16 wherein the acoustic wave device is configured to suppress a second harmonic response of the acoustic wave filter.
19 . The acoustic wave filter of claim 16 wherein the acoustic wave device is configured to increase power handling of the acoustic wave filter.
20 . The acoustic wave filter of claim 16 wherein the first piezoelectric layer has a different doping concentration than the second piezoelectric layer.