Group III nitride semiconductor light-emitting device
An object of the present invention is to provide a Group III nitride semiconductor light-emitting device with high emission efficiency. The inventive Group III nitride semiconductor light-emitting device has an n-type layer, a light-emitting layer and a p-type layer composed of a Group III nitride semiconductor on a substrate, with the light-emitting layer sandwiched between the n-type layer and p-type layer, wherein the range for Δa as the ratio of the difference between the a-axis lattice constant of the layer between the light-emitting layer and substrate (or in the case of multiple layers with different compositions between the light-emitting layer and substrate, where each layer is grouped according to composition, the a-axis lattice constant of the group having the maximum thickness considering all of the layers belonging to the group) a 1 and the a-axis lattice constant of the light-emitting layer (or if the light-emitting layer has a multiple quantum well structure, the a-axis lattice constant determined from the zero-order peak representing the average composition of the well layers and barrier layers) a 2 , represented by the following formula (I), is −0.05≦Δa≦0.05 (unit: %). Δ a =100( a 1 - a 2 )/ a 1 (I)
1. A Group III nitride semiconductor light-emitting device having an n-type layer, a light-emitting layer and a p-type layer composed of a Group III nitride semiconductor on a substrate, with the light-emitting layer sandwiched between the n-type layer and p-type layer, wherein the range for Δa as the ratio of the difference between the a-axis lattice constant of the layer between the light-emitting layer and substrate (or in the case of multiple layers with different compositions between the light-emitting layer and substrate, where each layer is grouped according to composition, the a-axis lattice constant of the group having the maximum thickness considering all of the layers belonging to the group) a 1 and the a-axis lattice constant of the light-emitting layer (or if the light-emitting layer has a multiple quantum well structure, the a-axis lattice constant determined from the zero-order peak representing the average composition of the well layers and barrier layers) a 2 , represented by the following formula (I), is −0.05≦Δa≦0.05 (unit: %)
Δ a= 100( a 1 - a 2 )/ a 1 (I).
2. A Group III nitride semiconductor light-emitting device according to claim 1 , wherein the Group III nitride semiconductor is represented by the formula Al X Ga Y In Z N 1-A M A (0≦X≦1, 0≦Y≦1, 0≦Z≦1 and X+Y+Z=1, wherein M represents a Group V element different from nitrogen (N), and 0≦A<1).
3. A Group III nitride semiconductor light-emitting device according to claim 1 , wherein the substrate is sapphire.
4. A Group III nitride semiconductor light-emitting device according to claim 1 , wherein the layer between the light-emitting layer and the substrate (or in the case of multiple layers with different compositions between the light-emitting layer and substrate, where each layer is grouped according to composition, the group having the maximum thickness considering all of the layers belonging to the group) is an n-type GaN layer.
5. A Group III nitride semiconductor light-emitting device according to claim 1 , wherein the light-emitting layer has a multiple quantum well structure.
6. A Group III nitride semiconductor light-emitting device according to claim 5 , wherein the barrier layer of the multiple quantum well structure is composed of Al X Ga Y In Z N (0≦X≦1, 0≦Y≦1, 0≦Z≦1, X+Y+Z=1), and the well layer is composed of Ga Y In Z N (0≦Y≦1, 0≦Z≦1, Y+Z=1).
7. A Group III nitride semiconductor light-emitting device according to claim 1 , wherein the substrate is sapphire, the layer between the light-emitting layer and the substrate (or in the case of multiple layers with different compositions between the light-emitting layer and substrate, where each layer is grouped according to composition, the group having the maximum thickness considering all of the layers belonging to the group) is an n-type GaN layer, the light-emitting layer has a multiple quantum well structure wherein the barrier layer is composed of Al X Ga Y In Z N (0≦X≦1, 0≦Y≦1, 0≦Z≦1, X+Y+Z=1) and the well layer is composed of Ga Y In Z N (0<Y<1, 0<Z<1, Y+Z=1), and the lattice constants a 1 and a 2 are larger than 3.181 Å.
8. A Group III nitride semiconductor light-emitting device according to claim 1 , wherein the thickness of the layer between the light-emitting layer and the substrate (or in the case of multiple layers with different compositions between the light-emitting layer and substrate, where each layer is grouped according to composition, the group having the maximum thickness considering all of the layers belonging to the group) is 1-20 μm.
9. A lamp comprising a Group III nitride semiconductor light-emitting device according to claim 1 .