Aluminum nitride dopant scheme for bulk acoustic wave filters

1. An acoustic wave resonator comprising a piezoelectric material formed of aluminum nitride (AlN) doped with one or more of beryllium (Be), strontium (Sr), and sodium (Na) to enhance performance of the acoustic wave resonator, the one or more of Be, Sr, and Na being charge balanced with at least one of Si and Ge, the piezoelectric material having a chemical formula of one of:

Al 1-2x Sr x Si x N (0 <x <1);

Al 1-2x Sr x Ge x N (0 <x <1);

Al 1-2x Be x Si x N (0 <x <1);

Al 1-2x Be x Ge x N (0 <x <1);

Al 1-3x Na x Si 2x N (0 <x <1); or

Al 1-3x Na x Ge 2x N (0 <x <1).

2. An acoustic wave filter including the acoustic wave resonator of claim 1 .

3. The acoustic wave filter of claim 2 comprising a bulk acoustic wave (BAW) resonator including the doped AlN.

4. The acoustic wave filter of claim 3 wherein the BAW resonator is one of a film bulk acoustic wave resonator, a Lamb wave resonator, or a solidly mounted resonator.

5. The acoustic wave filter of claim 3 comprising a radio frequency filter.

6. An electronics module including the radio frequency filter of claim 5 .

7. An electronic device including the electronics module of claim 6 .

8. The acoustic wave resonator of claim 1 wherein the piezoelectric material has a Wurtzite crystal structure.

9. A method of forming an acoustic wave resonator comprising depositing electrodes on a piezoelectric film formed of aluminum nitride (AlN) doped with one or more of beryllium (Be), strontium (Sr), and sodium (Na), the one or more of Be, Sr, and Na being charge balanced with at least one of Si and Ge, the material of the piezoelectric film having a chemical formula of one of:

Al 1-2x Sr x Si x N (0 <x <1);

Al 1-2x Sr x Ge x N (0 <x <1);

Al 1-2x Be x Si x N (0 <x <1);

Al 1-2x Be x Ge x N (0 <x <1);

Al 1-3x Na x Si 2x N (0 <x <1); or

Al 1-3x Na x Ge 2x N (0 <x <1).

10. The method of claim 9 wherein depositing the electrodes on the piezoelectric film includes depositing a first electrode on a top surface of the piezoelectric film and depositing a second electrode on a bottom surface of the piezoelectric film.

11. The method of claim 10 wherein the acoustic wave resonator is a film bulk acoustic wave resonator and the method further comprises defining a cavity below the bottom surface of the piezoelectric film.

12. The method of claim 10 wherein the acoustic wave resonator is a Lamb wave resonator and depositing the first electrode on the top surface of the piezoelectric film comprises depositing interdigital transducer electrodes on the top surface of the piezoelectric film.

13. The method of claim 10 wherein the acoustic wave resonator is a solidly mounted resonator and the method further comprises forming the piezoelectric film on a top surface of a Bragg reflector.

14. A piezoelectric material comprising aluminum nitride (AlN) doped with one or more of beryllium (Be), strontium (Sr), and sodium (Na), the one or more of Be, Sr, and Na being charge balanced with at least one of Si and Ge, the piezoelectric material having a chemical formula of one of:

Al 1-2x Sr x Si x N (0 <x <1);

Al 1-2x Sr x Ge x N (0 <x <1);

Al 1-2x Be x Si x N (0 <x <1);

Al 1-2x Be x Ge x N (0 <x <1);

Al 1-3x Na x Si 2x N (0 <x <1); or

Al 1-3x Na x Ge 2x N (0 <x <1).

15. The piezoelectric material of claim 14 having a Wurtzite crystal structure.