III-nitride light emitting device with double heterostructure light emitting region

1. A semiconductor light emitting device comprising:

an n-type region;

a p-type region; and

a light emitting region disposed between the n-type region and the p-type region in a double-heterostructure that includes only a single III-nitride light emitting layer, this light emitting layer being the only layer in the device from which light is produced when current flows between the n-type and p-type regions;

wherein the light emitting layer has a thickness between 100 Å and 600 Å, and at least a portion of the light emitting layer has a graded composition,

wherein an InN composition in the light emitting layer is graded from a first InN composition in a first portion of the light emitting layer closest to the n-type region to a second InN composition in a second portion of the light emitting layer closest to the p-type region, wherein the first InN composition is greater than the second InN composition,

wherein the InN composition is graded linearly from the first InN composition to the second InN composition.

2. The semiconductor light emitting device of claim 1 wherein the light emitting layer is InGaN.

3. The semiconductor light emitting device of claim 1 wherein the light emitting layer is doped with an n-type dopant.

4. The semiconductor light emitting device of claim 1 wherein the light emitting layer has a thickness between 100 Å and 250 Å.

5. The semiconductor light emitting device of claim 1 further comprising a step change in InN composition between the light emitting layer and a portion of the n-type region.

6. The semiconductor light emitting device of claim 1 , including a preparation layer that includes indium and is disposed between the n-type region and the light emitting region; wherein the first InN composition is greater than an InN composition in the preparation layer.

7. The semiconductor light emitting device of claim 1 , including a preparation layer that includes indium and is disposed between the n-type region and the light emitting region.

8. The semiconductor light emitting device of claim 7 , including a spacer layer disposed between the preparation layer and the light emitting region.

9. The semiconductor light emitting device of claim 7 , wherein the preparation layer is an n-type layer.

10. The semiconductor light emitting device of claim 7 , wherein the preparation layer includes 2% to 12% InN.

11. The semiconductor light emitting device of claim 7 , wherein the preparation layer includes 2% to 6% InN.

12. The semiconductor light emitting device of claim 1 , including a blocking layer that includes a compound of AlN and is disposed between the p-type region and the III-nitride light emitting region.

13. The semiconductor light emitting device of claim 12 , wherein the blocking layer comprises Al x Ga 1-x N, and x is greater than 0.08.

14. The semiconductor light emitting device of claim 13 , wherein the blocking layer comprises Al x Ga 1-x N, and x is less than 0.30.

15. The semiconductor light emitting device of claim 12 , wherein the blocking layer is at least 10 Angstroms thick.

16. The semiconductor light emitting device of claim 15 , wherein the blocking layer is less than 1000 Angstroms thick.

17. A semiconductor light emitting device comprising:

an n-type region;

a p-type region; and

a light emitting region disposed between the n-type region and the p-type region in a double-heterostructure that includes only a single III-nitride light emitting layer, this light emitting layer being the only layer in the device from which light is produced when current flows between the n-type and p-type regions;

wherein the light emitting layer has a thickness between 100 Å and 600 Å, and at least a portion of the light emitting layer has a graded composition,

wherein the composition of the light emitting layer is graded monotonically across the light emitting layer.

18. A semiconductor light emitting device comprising:

an n-type region;

a p-type region;

a light emitting region disposed between the n-type region and the p-type region in a double-heterostructure that includes only a single III-nitride light emitting layer, this light emitting layer being the only layer in the device from which light is produced when current flows between the n-type and p-type regions;

a preparation layer that includes indium and is disposed between the n-type region and the light emitting region;

a first spacing layer that does not include Al and is disposed between the preparation layer and the light emitting region;

a blocking layer that includes a compound of AlN and is disposed between the p-type region and the III-nitride light emitting region; and

a second spacing layer that does not include Al and is disposed between the blocking layer and the III-nitride light emitting region;

wherein the light emitting layer has a thickness between 100 Å and 600 Å, and at least a portion of the light emitting layer has a graded composition.

19. The semiconductor light emitting device of claim 18 , wherein the preparation layer includes 2% to 12% InN.