Controlled polarity group III-nitride films and methods of preparing such films
The present invention provides methods of preparing Group III-nitride films of controlled polarity and substrates coated with such controlled polarity films. In particular, the invention provides substrate preparation steps that optimize the substrate surface for facilitating growth of a Group III-polar film, an N-polar film, or a selectively patterned film with both a Group III-polar portion and an N-polar portion in precise positioning. The methods of the invention are particularly suited for use in CVD methods.
1. A coated substrate comprising:
(a) a substrate having a surface; and
(b) a selectively patterned chemical vapor deposition (CVD) grown Group III-nitride film comprising both a Group III-polar portion and an N-polar portion deposited on the surface of the substrate;
wherein the Group III-polar portion of the deposited film has an rms roughness of less than about 4 nm and the N-polar portion of the deposited film has an rms roughness of less than about 4 nm; and
wherein the surface of the Group III-nitride film is smooth and continuously even across both the Group III-polar portion of the film and the N-polar portion of the film.
2. The coated substrate of claim 1 , wherein the substrate comprises c-plane sapphire.
3. The coated substrate of claim 1 , wherein the substrate comprises a Group III material.
4. The coated substrate of claim 1 , wherein the substrate comprises silicon carbide.
5. The coated substrate of claim 1 , wherein the Group III-nitride is selected from the group consisting of Aluminum nitride, Gallium nitride, and Indium nitride.
6. The coated substrate of claim 1 , wherein the coated substrate is a hetero structure.
7. A device comprising a coated substrate according to claim 1 .
8. A substrate having a dual polarity chemical vapor deposition (CVD) grown Group III-nitride film coated thereon, the substrate having a portion comprising a nitridation layer and a portion comprising a buffer layer, wherein the portion of the Group III-nitride film deposited on the nitridation layer is N-polar and has an rms roughness of less than about 4 nm, and the portion of the Group III-nitride film deposited on the buffer layer is Group III-polar and has an rms roughness of less than about 4 nm; wherein the surface of the Group III-nitride film is smooth and continuously even across both the Group III-polar portion of the film and the N-polar portion of the film.
9. The coated substrate of claim 8 , wherein the substrate comprises c-plane sapphire.
10. The coated substrate of claim 8 , wherein the substrate comprises a Group III material.
11. The coated substrate of claim 8 , wherein the substrate comprises silicon carbide.
12. The coated substrate of claim 8 , wherein the Group III-nitride is selected from the group consisting of Aluminum nitride, Gallium nitride, and Indium nitride.
13. The coated substrate of claim 8 , wherein the substrate is coated by a method comprising:
(a) performing a first nitridation of the substrate to cover the surface of the substrate with a nitridation layer;
(b) applying a buffer layer to the surface of the substrate with the nitridation layer thereon;
(c) annealing the buffer layer;
(d) selectively patterning the substrate surface comprising selectively removing a portion of the buffer layer from the substrate surface;
(e) optionally, annealing the selectively patterned substrate surface;
(f) performing a second nitridation of the substrate such that a portion of the substrate is covered with an exposed nitridation layer and a portion of the substrate surface is covered with a buffer layer; and
(g) depositing a Group III-nitride film on the substrate such that the film deposited on the portion of the substrate with the exposed nitridation layer is N-polar, and the film deposited on the portion of the substrate with an exposed buffer layer is Group III-polar, and such that the N-polar portion and the Group III-polar portion are grown simultaneously such that the respective growth rates differ by less than about 10%.
14. A device comprising a coated substrate according to claim 8 .
15. A polarity-controlled, patterned Group III-nitride film comprising a Group III-polar portion having an rms roughness of less than about 4 nm and an N-polar portion having an rms roughness of less than about 4 nm, wherein the Group III-polar portion and the N-polar portion were simultaneously grown such that the surface of the Group III-nitride film is smooth and continuously even across both the Group III-polar portion of the film and the N-polar portion of the film.