Acoustic wave devices with improved heat management
An acoustic wave device can have a plurality of coupling portions configured to electrically couple electrodes of the device to the substrate of the device to provide a bypass current pathway through the substrate for heat management. The substrate can be a semiconductor material, which can become more conductive as the temperature increases so that the bypass current pathway diverts more power through the substrate as the temperature increases. The acoustic wave device can be a surface acoustic wave device, which can have an interdigital transducer electrode that has the coupling portions on each of the bus bars and extending through the piezoelectric layer to contact the substrate. The acoustic wave device can be a bulk acoustic wave device in some implementations.
1 . An acoustic wave device comprising:
a substrate that decreases in electrical resistivity in response to an increase in temperature;
a dielectric layer over the substrate;
a piezoelectric layer over the dielectric layer;
a first electrode between the substrate and the piezoelectric layer, the first electrode having a first coupling portion that extends through at least a part of the dielectric layer towards the substrate to electrically couple the first electrode to the substrate;
a second electrode, the piezoelectric layer between the first electrode and the second electrode, the second electrode having a second coupling portion that extends through at least part of the dielectric layer towards the substrate to electrically couple the second electrode to the substrate;
a first electrical pathway that transfers electrical current from the first electrode to the second electrode through the piezoelectric layer; and
a second electrical pathway that transfers electrical current from the first electrode to the second electrode through the first coupling portion, the substrate, and the second coupling portion to bypass the first electrical pathway based at least in part on the temperature of the substrate.
2 . The device of claim 1 , wherein the substrate is made of a semiconductor material.
3 . The device of claim 1 , wherein the substrate is made of silicon.
4 . The device of claim 1 , further comprising an acoustic reflector between the piezoelectric layer and the substrate and the second electrical pathway transfers electrical current from the first electrode to the second electrode through a portion of the substrate that is under the acoustic reflector.
5 . The device of claim 1 , wherein the second coupling portion extends completely through the piezoelectric layer.
6 . The device of claim 1 , wherein the first and second coupling portions are in direct contact with the substrate.
7 . The device of claim 1 , wherein the first and second coupling portions are in ohmic contact with the substrate.
8 . The device of claim 1 , wherein the first and second coupling portions are capacitively coupled to the substrate.
9 . The device of claim 1 , wherein the first and second coupling portions extend completely through the dielectric layer.
10 . The device of claim 1 , wherein the device is a bulk acoustic wave device.
11 . An acoustic wave device comprising:
a substrate that decreases in electrical resistivity in response to an increase in temperature;
a dielectric layer over the substrate;
a piezoelectric layer over the dielectric layer;
a first electrode below a first surface of the piezoelectric layer, the first electrode having a first coupling portion that extends through at least a part of the dielectric layer towards the substrate to electrically couple the first electrode to the substrate;
a second electrode above a second surface of the piezoelectric layer, the second surface on an opposite side of the first surface of the piezoelectric layer, the second electrode having a second coupling portion that extends through at least a part of the dielectric layer towards the substrate to electrically couple the second electrode to the substrate;
a first electrical pathway that transfers electrical current from the first electrode to the second electrode through the piezoelectric layer; and
a second electrical pathway that transfers electrical current from the first electrode to the second electrode through the first coupling portion, the substrate, and the second coupling portion, the second electrical pathway conducting more electrical current when the temperature of the substrate increases.
12 . The device of claim 11 , wherein the substrate is made of a semiconductor material.
13 . The device of claim 11 , wherein at least one of the first and second coupling portions extends completely through the piezoelectric layer.
14 . The device of claim 11 , wherein the first and second coupling portions are in direct contact with the substrate.
15 . The device of claim 11 , wherein the first and second coupling portions are in ohmic contact with the substrate.
16 . The device of claim 11 , wherein the first and second coupling portions are capacitively coupled to the substrate.
17 . The device of claim 11 , wherein the first and second coupling portions extend completely through the dielectric layer.
18 . The device of claim 11 , wherein the device is a bulk acoustic wave device.
19 . The device of claim 11 , wherein the device is a surface acoustic wave device.
20 . A method of operating an acoustic wave device, the method comprising:
transferring electrical current from a first electrode to a second electrode via a first electrical pathway through a piezoelectric layer that is between first electrode and the second electrode;
transferring electrical current from the first electrode to the second electrode via a second electrical pathway through a substrate below the first electrode, the second electrical pathway including a first coupling portion that extends from the first electrode through at least a portion of a dielectric layer towards the substrate to electrically couple with the substrate, and a second coupling portion that extends from the second electrode through at least a portion of the dielectric layer towards the substrate to electrically couple with the substrate; and
bypassing the first electrical pathway with the second electrical pathway based at least in part on temperature of the substrate.