Substituted aluminum nitride for improved acoustic wave filters

1. An acoustic wave resonator comprising a piezoelectric material formed of aluminum nitride doped with calcium to enhance performance of the acoustic wave resonator, wherein the calcium is charge balanced with at least one of silicon and germanium and the piezoelectric material has a chemical formula of one of

Al 1−2x Ca x Si x N (0< x< 1); or

Al 1−2x Ca x Ge x 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 wherein the acoustic wave resonator is a bulk acoustic wave resonator.

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

5. The acoustic wave filter of claim 3 wherein the acoustic wave filter is a radio frequency filter.

6. An electronics module including the acoustic wave 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: forming a piezoelectric film formed of aluminum nitride doped with calcium, wherein the calcium is charge balanced with at least one of silicon and germanium and the piezoelectric material has a chemical formula of one of

Al 1−2x Ca x Si x N (0< x< 1); or

Al 1−2x Ca x Ge x N (0< x< 1); and

depositing electrodes on the piezoelectric film to form the acoustic wave resonator.

10. The method of claim 9 wherein depositing the electrodes on the piezoelectric film in 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. An acoustic wave resonator including a film of piezoelectric material and an electrode disposed on the film of piezoelectric material, the film of piezoelectric material comprising:

AlN doped with cations of one or more elements selected from the group consisting of:

a) one of Sb, or Nb;

b) Cr in combination with one or more of B, Sc, Y, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, or Yb;

c) one of Nb and Ta in combination with one of Li, Ca, Ni, or Co;

d) Ca in combination with one of Si or Ge;

e) Mg in combination with one of Si or Ge; or

f) one or more of Co, Sb, Ta, Nb, Si, or Ge in combination with one or more of Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, or Yb;

the cations at least partially substituting for Al in a crystal structure of the piezoelectric material.

15. The acoustic wave resonator of claim 14 wherein the piezoelectric material has a Wurtzite crystal structure.

16. The acoustic wave resonator of claim 14 configured as a solidly mounted resonator.

17. The acoustic wave resonator of claim 14 configured as a film bulk acoustic resonator.

18. A filter including the acoustic wave resonator of claim 14 .

19. The filter of claim 18 having a passband in the radio frequency band.

20. An electronic device module including the filter of claim 18 .

21. An electronic device including the electronic device module of claim 20 .

22. The electronic device of claim 21 wherein the electronic device module is a radio frequency electronic device module.