Nitride based quantum well light-emitting devices having improved current injection efficiency
A III-nitride based device provides improved current injection efficiency by reducing thermionic carrier escape at high current density. The device includes a quantum well active layer and a pair of multi-layer barrier layers arranged symmetrically about the active layer. Each multi-layer barrier layer includes an inner layer abutting the active layer; and an outer layer abutting the inner layer. The inner barrier layer has a bandgap greater than that of the outer barrier layer. Both the inner and the outer barrier layer have bandgaps greater than that of the active layer. InGaN may be employed in the active layer, AlInN, AlInGaN or AlGaN may be employed in the inner barrier layer, and GaN may be employed in the outer barrier layer. Preferably, the inner layer is thin relative to the other layers. In one embodiment the inner barrier and active layers are 15 Å and 24 Å thick, respectively.
1. A III-nitride based semiconductor device comprising:
a quantum well active layer of a first nitride-based material having a first bandgap characteristic; and
a pair of multi-layer barrier layers arranged symmetrically in abutting relationship with said quantum well active layer, each of said pair of multi-layer barrier layers comprising:
an inner layer abutting said quantum well active layer, said inner layer being formed of a second nitride-based material having a second bandgap characteristic greater than said first bandgap characteristic; and
an outer layer abutting said inner layer, said outer layer being formed of a third nitride-based material having a third bandgap characteristic greater than said first bandgap characteristic and less than said second bandgap characteristic, said outer barrier layer having a thickness and material composition causing it to function primarily as a barrier layer and not as a light guiding layer.
2. The III-nitride based semiconductor device of claim 1 , wherein each of said inner layers is thin relative to each of said outer layers.
3. The III-nitride based semiconductor device of claim 2 , wherein each of said inner layers has a thickness measuring approximately 15 Å or less.
4. The III-nitride based semiconductor device of claim 3 , wherein each of said inner layers comprises AlInN.
5. The III-nitride based semiconductor device of claim 3 , wherein each of said inner layers comprises AlGaN.
6. The III-nitride based semiconductor device of claim 3 , wherein each of said inner layers comprises AlInGaN.
7. The III-nitride based semiconductor device of claim 1 , wherein said quantum well active layer comprises InGaN.
8. The III-nitride based semiconductor device of claim 1 , wherein each of said outer layers comprises GaN.
9. The III-nitride based semiconductor device of claim 1 , wherein each one of said inner barrier layers has a thickness measuring approximately 5 Å to approximately 15 Å, and wherein each one of said outer barrier layers has a thickness measuring approximately 50 Å to approximately 150 Å.
10. A III-nitride based semiconductor device comprising:
a quantum well active layer of InGaN;
a pair of multi-layer barrier layers arranged symmetrically in abutting relationship with said quantum well active layer, each of said pair of multi-layer barrier layers comprising:
a thin inner layer abutting said quantum well active layer, said thin inner layer having a thickness of less than approximately 15 Å and being formed of a material selected from the group consisting of AlInN, AlInGaN, and AlGaN; and
a thick outer layer abutting said thin inner layer, said thick layer being formed of u-GaN and being thicker than said thin inner layer.
11. The III-nitride based semiconductor device of claim 10 , wherein said quantum well active layer has a thickness measuring approximately 20 Å to approximately 50 Å, each of said thin inner layers having a thickness measuring approximately 5 Å to approximately 15 Å, and each of said thick outer layer having a thickness measuring approximately 50 Å to approximately 100 Å.