Group III nitride semiconductor light-emitting device including a superlatice layer
A Group III nitride semiconductor light-emitting device includes at least an n-type-layer-side cladding layer, a light-emitting layer, and a p-type-layer-side cladding layer, each of the layers being formed of a Group III nitride semiconductor. The n-type-layer-side cladding layer is a superlattice layer having a periodic structure including an In y Ga 1-y N (0<y<1) layer, an Al x Ga 1-x N (0<x<1) layer, and a GaN layer. The n-type-layer-side cladding layer has a four-layer periodic structure including a second GaN layer interposed between the In y Ga 1-y N (0<y<1) layer and the Al x Ga 1-x N (0<x<1) layer.
1. A Group III nitride semiconductor light-emitting device comprising:
an n-type-layer-side cladding layer, a light-emitting layer, and a p-type-layer-side cladding layer, each of the layers comprising a Group III nitride semiconductor,
wherein the n-type-layer-side cladding layer comprises a superlattice layer having a periodic structure comprising four layers as one periodic unit,
wherein the periodic unit comprises a first GaN layer, an In y Ga 1-y N (0<y<1) layer, a second GaN layer with a thickness of 0.3 nm to 2.5 nm, and an Al x Ga 1-x N (0<x<1) layer,
wherein the second GaN layer is interposed between the In y Ga 1-y N (0<y<1) layer and the Al x Ga 1-x N (0<x<1) layer,
wherein the Al x Ga 1-x N (0<x<1) layer has a thickness of 0.3 nm to 2.5 nm such that electrons tunnel through the Al x Ga 1-x N layer,
wherein the Al x Ga 1-x N (0<x<1) layer has an Al compositional proportion x of 0.05 or more and less than 1,
wherein the light-emitting layer comprises a multiple quantum well structure comprising a first AlGaN layer, an InGaN layer, a GaN layer and a second AlGaN layer having an Al compositional proportion higher than the first AlGaN layer as one periodic unit,
wherein the p-type-layer-side cladding layer comprises a superlattice layer having a periodic structure comprising an In w Ga 1-w N layer and an Al z Ga 1-z N (0<z<1) layer,
wherein the Al x Ga 1-x N (0<x<1) layer of the n-type-layer-side cladding layer has a compositional proportion x not less than ½ of the compositional proportion z of the Al z Ga 1-z N (0<z<1) layer of the p-type-layer-side cladding layer, and
wherein the light-emitting layer is formed directly on the n-type-layer-side cladding layer.
2. A Group III nitride semiconductor light-emitting device according to claim 1 , wherein the second GaN layer is undoped.
3. A Group III nitride semiconductor light-emitting device according to claim 1 , wherein the first GaN layer is doped with Si.
4. A Group III nitride semiconductor light-emitting device according to claim 2 , wherein the first GaN layer is doped with Si.
5. A Group III nitride semiconductor light-emitting device according to claim 1 , wherein the first GaN layer is undoped.
6. A Group III nitride semiconductor light-emitting device according to claim 1 , wherein the periodic structure of the n-type-layer-side cladding layer has 3 to 30 periodic units.
7. A Group III nitride semiconductor light-emitting device according to claim 1 , wherein the second GaN layer is deposited on the In y Ga 1-y N (0<y<1) layer and the first GaN layer is deposited on the Al x Ga 1-x N (0<x<1) layer.
8. A Group III nitride semiconductor light-emitting device according to claim 4 , wherein the second GaN layer is deposited on the In y Ga 1-y N (0<y<1) layer and the first GaN layer is deposited on the Al x Ga 1-x N (0<x<1) layer.
9. A Group III nitride semiconductor light-emitting device according to claim 1 , wherein the In y Ga 1-y N (0<y<1) layer, the Al x Ga 1-x N (0<x<1) layer or the second GaN layer contains Si.