Piezoelectric member that achieves high sound speed, acoustic wave apparatus, and piezoelectric member manufacturing method
A piezoelectric member that achieves a high sound speed includes a silicon-containing substrate and a piezoelectric layer. The piezoelectric layer is disposed on the silicon-containing substrate. At least a surface layer of the piezoelectric layer on a side opposite to the silicon-containing substrate is made of B x Al 1-x N (0<x≦0.2).
1. A piezoelectric member comprising:
a silicon-containing substrate; and
a piezoelectric layer disposed on the silicon-containing substrate; wherein
at least a surface layer of the piezoelectric layer on a side opposite to the silicon-containing substrate is made of B x Al 1-x N, wherein 0<x≦0.2, wherein
a portion of the piezoelectric layer made of B x Al 1-x N contains a wurtzite-type crystal of B x Al 1-x N, and
the portion of the piezoelectric layer made of B x Al 1-x N is C-axis oriented so that a (0001) plane is parallel to a surface of the silicon-containing substrate.
2. The piezoelectric member according to claim 1 , further comprising an aluminum nitride layer disposed between the silicon-containing substrate and the piezoelectric layer.
3. The piezoelectric member according to claim 2 , further comprising a Mo metal layer disposed between the aluminum nitride layer and the piezoelectric layer.
4. The piezoelectric member according to claim 3 , further comprising another aluminum nitride layer disposed between the Mo metal layer and the piezoelectric layer.
5. The piezoelectric member according to claim 2 , wherein the aluminum nitride layer contains a wurtzite-type crystal of aluminum nitride.
6. The piezoelectric member according to claim 2 , wherein a thickness of the Mo metal layer is about 10 nm to about 500 nm.
7. The piezoelectric member according to claim 2 , wherein the thickness of the aluminum nitride layer is about 10 nm or more.
8. The piezoelectric member according to claim 1 , wherein a thickness of the piezoelectric layer is about 50 nm to about 5000 nm.
9. The piezoelectric member according to claim 1 , further comprising a low sound speed layer disposed on the piezoelectric layer having a sound speed lower than that of the piezoelectric layer.
10. An acoustic wave apparatus comprising the piezoelectric member according to claim 1 .
11. The acoustic wave apparatus according to claim 10 , wherein the acoustic wave apparatus is one of an acoustic wave apparatus and a bulk acoustic wave apparatus.
12. The piezoelectric member according to claim 1 , wherein the piezoelectric layer is formed by a sputtering method.
13. The piezoelectric member according to claim 1 , further comprising an aluminum nitride layer disposed between the silicon-containing substrate and the piezoelectric layer.
14. The piezoelectric member according to claim 13 , wherein the thickness of the aluminum nitride layer is about 10 nm or more.
15. The piezoelectric member according to claim 1 , further comprising an aluminum nitride layer disposed between the silicon-containing substrate and the piezoelectric layer.
16. The piezoelectric member according to claim 1 , wherein 0.03≦x≦0.18.