Reverse polarization light emitting region for a semiconductor light emitting device
View Patent ↗A semiconductor light emitting device includes a light emitting layer disposed between an n-type region and a p-type region. The light emitting layer may be a wurtzite III-nitride layer with a thickness of at least 50 angstroms. The light emitting layer may have a polarization reversed from a conventional wurtzite III-nitride layer, such that across an interface between the light emitting layer and the p-type region, the wurtzite c-axis points toward the light emitting layer. Such an orientation of the c-axis may create a negative sheet charge at an interface within or at the edge of the p-type region, providing a barrier to charge carriers in the light emitting layer.
1. A structure comprising:
a semiconductor light emitting layer disposed between a p-type region and an n-type region, wherein:
the light emitting layer comprises a wurtzite crystal structure;
the light emitting layer has a thickness of at least 50 angstroms; and
across an interface disposed between the light emitting layer and the p-type region, a wurtzite c-axis, defined as pointing from a nitrogen face of a III-nitride unit cell to a gallium face of a III-nitride unit cell, points toward the light emitting layer.
2. The structure of claim 1 wherein the light emitting layer has a thickness between 50 and 500 angstroms.
3. The structure of claim 1 wherein the light emitting layer has a thickness between 60 and 300 angstroms.
4. The structure of claim 1 wherein the light emitting layer has a thickness between 75 and 175 angstroms.
5. The structure of claim 1 wherein the light emitting layer has a thickness greater than 100 angstroms.
6. The structure of claim 1 wherein the light emitting layer is a III-nitride layer.
7. The structure of claim 1 wherein the light emitting layer is InGaN.
8. The structure of claim 1 wherein the light emitting layer is AlGaN.
9. The structure of claim 1 wherein the light emitting layer has a dislocation density less than 10 9 /cm 2 .
10. The structure of claim 1 wherein the light emitting layer has a dislocation density less than 10 8 /cm 2 .
11. The structure of claim 1 wherein the light emitting layer has a dislocation density less than 10 7 /cm 2 .
12. The structure of claim 1 wherein the light emitting layer has a dislocation density less than 10 6 /cm 2 .
13. The structure of claim 1 further comprising a GaN substrate, wherein the n-type region is disposed between the GaN substrate and the light emitting layer.
14. The structure of claim 13 wherein across an interface disposed between the GaN substrate and the n-type region, a wurtzite crystal c-axis points toward the GaN substrate.
15. The structure of claim 1 wherein the n-type region is a first n-type region, the structure further comprising a tunnel junction and a second n-type region, wherein the tunnel junction is disposed between the second n-type region and the p-type region.
16. The structure of claim 15 wherein the p-type region is grown before the light emitting layer.
17. The structure of claim 1 wherein the light emitting layer, p-type region, and n-type region are bonded to a host substrate by a bond disposed proximate the n-type region.
18. The structure of claim 1 further comprising a first lead electrically connected to the n-type region, a second lead electrically connected to the p-type region, and a cover disposed over the light emitting layer.
19. A structure comprising:
a semiconductor light emitting layer;
an n-type region;
a p-type region, the p-type region comprising a barrier layer having a band gap greater than a band gap in the light emitting layer, such that an edge of the barrier layer forms a barrier to charge carriers in the light emitting layer; and
a negative polarization-induced charge at the barrier; wherein:
the light emitting layer is disposed between the n-type region and the p-type region; and
the light emitting layer has a thickness of at least 50 angstroms.
20. The structure of claim 19 wherein the light emitting layer has a thickness between 50 and 500 angstroms.
21. The structure of claim 19 wherein the light emitting layer has a thickness between 60 and 175 angstroms.
22. The structure of claim 19 wherein the light emitting layer is a III-nitride layer.
23. The structure of claim 19 further comprising a first lead electrically connected to the n-type region, a second lead electrically connected to the p-type region, and a cover disposed over the light emitting layer.
24. The structure of claim 19 wherein the barrier layer is n-type or undoped and the barrier comprises an interface between the barrier layer and a p-type layer in the p-type region.