Group III nitride semiconductor light-emitting device and method for producing the same
The invention provides a Group III nitride semiconductor light-emitting device in which the strain in the light-emitting layer is relaxed, thereby attaining high light emission efficiency, and a method for producing the device. The light-emitting device of the present invention has a substrate, a low-temperature buffer layer, an n-type contact layer, a first ESD layer, a second ESD layer, an n-side superlattice layer, a light-emitting layer, a p-side superlattice layer, a p-type contact layer, an n-type electrode N 1 , a p-type electrode P 1 , and a passivation film F 1 . The second ESD layer has pits X having a mean pit diameter D. The mean pit diameter D is 500 Å to 3,000 Å. An InGaN layer included in the n-side superlattice layer has a thickness Y satisfying the following condition: −0.029×D+82.8≦Y≦−0.029×D+102.8.
1. A Group III nitride semiconductor light-emitting device comprising an underlying layer formed of a Group III nitride semiconductor, a superlattice layer formed on the underlying layer, and a light-emitting layer formed on the superlattice layer, wherein:
the underlying layer has pits;
the superlattice layer has at least an Indium-containing layer formed of an Indium-containing Group III nitride semiconductor;
the pits have a mean pit diameter D (Å) as measured at the interface between the underlying layer and the superlattice layer which pit diameter satisfies the following condition: 500 Å≦D≦3,000 Å; and
the Indium-containing layer has a thickness Y (Å) satisfying the following condition:
−0.029 ×D+ 82.8 ≦Y≦− 0.029 ×D+ 102.8.
2. The Group III nitride semiconductor light-emitting device according to claim 1 , wherein:
the superlattice layer is formed of repeatedly deposited layer units;
each layer unit has two or more Indium-containing layers; and
the thickness Y (Å) of the Indium-containing layer is that measured for a layer of the superlattice layer having the smallest bandgap.
3. The Group III nitride semiconductor light-emitting device according to claim 2 , wherein the bottom ends of the pits are located within the thickness of the underlying layer.
4. The Group III nitride semiconductor light-emitting device according to claim 3 , wherein the underlying layer is an electrostatic-breakdown-voltage-improving layer for preventing electrostatic breakdown of each semiconductor layer.
5. The Group III nitride semiconductor light-emitting device according to claim 3 , wherein the mean pit diameter D (Å) satisfies the following condition:
500 Å≦D≦ 1,500 Å.
6. The Group III nitride semiconductor light-emitting device according to claim 1 , wherein the bottom ends of the pits are located within the thickness of the underlying layer.
7. The Group III nitride semiconductor light-emitting device according to claim 6 , wherein the underlying layer is an electrostatic-breakdown-voltage-improving layer for preventing electrostatic breakdown of each semiconductor layer.
8. The Group III nitride semiconductor light-emitting device according to claim 6 , wherein the mean pit diameter D (Å) satisfies the following condition:
500 Å≦D≦ 1,500 Å.
9. The Group III nitride semiconductor light-emitting device according to claim 2 , wherein the underlying layer is an electrostatic-breakdown-voltage-improving layer for preventing electrostatic breakdown of each semiconductor layer.
10. The Group III nitride semiconductor light-emitting device according to claim 6 , wherein the mean pit diameter D (Å) satisfies the following condition:
500 Å≦D≦ 1,500 Å.
11. The Group III nitride semiconductor light-emitting device according to claim 1 , wherein the underlying layer is an electrostatic-breakdown-voltage-improving layer for preventing electrostatic breakdown of each semiconductor layer.
12. The Group III nitride semiconductor light-emitting device according to claim 1 , wherein the mean pit diameter D (Å) satisfies the following condition:
500 Å≦D≦ 1,500 Å.
13. A method for producing a Group III nitride semiconductor light-emitting device comprising:
forming an underlying layer,
forming a superlattice layer on the underlying layer, and
forming a light-emitting layer on the superlattice layer;
wherein, in formation of the underlying layer, pits are provided in the underlying layer such that the mean pit diameter D (Å) as measured at the interface between the underlying layer and the superlattice layer satisfies the following condition:
500 Å≦D≦ 3,000 Å; and,
in formation of the superlattice layer, an Indium-containing layer is formed from an Indium-containing Group III nitride semiconductor such that the Indium-containing layer has a thickness Y (Å) satisfying the following condition:
−0.029 ×D+ 82.8 ≦Y≦− 0.029 ×D+ 102.8.
14. The method for producing a Group III nitride semiconductor light-emitting device according to claim 13 , wherein, in formation of the superlattice layer,
layer units each having two or more Indium-containing layers are repeatedly deposited, and
an Indium-containing layer of the superlattice layer having the smallest bandgap is formed so as to have the thickness Y (Å) of the Indium-containing layer.
15. The method for producing a Group III nitride semiconductor light-emitting device according to claim 14 , wherein the mean pit diameter D (Å) is adjusted to satisfy the following condition: 500 Å≦D≦1,500 Å.
16. The method for producing a Group III nitride semiconductor light-emitting device according to claim 13 , wherein the mean pit diameter D (Å) is adjusted to satisfy the following condition: 500 Å≦D≦1,500 Å.