Nitride semiconductor ultraviolet light-emitting element
View Patent ↗An active layer including an AlGaN semiconductor layer having a band gap energy of 3.4 eV or higher and a p-type cladding layer configured of a p-type AlGaN semiconductor layer and located above the active layer are formed in a first region on the n-type cladding layer, the first region being in a plane parallel to a surface of the n-cladding layer configured of an n-type AlGaN semiconductor layer. An n-electrode metal layer making Ohmic contact with the n-type cladding layer is formed on an adjacent region to the first region in a second region which is a region other than the first region on the n-type cladding layer. A first reflective metal layer reflecting ultraviolet light emitted from the active layer is formed on a surface of the n-type cladding layer in the second region other than the adjacent region. The n-electrode metal layer is arranged between the first region and a region in which the first reflective metal layer contacts the surface of the n-type cladding layer.
1. A nitride semiconductor ultraviolet light-emitting element comprising:
an n-type cladding layer configured of an n-type AlGaN semiconductor layer;
the n-type cladding layer formed on a template allowing the ultraviolet light to pass therethrough and configured of an insulator layer, a semiconductor layer, or a laminated body configured of the insulator layer and the semiconductor layer, the template including an AlN layer;
an active layer including an AlGaN semiconductor layer having a band gap energy of 3.4 eV or higher;
a p-type cladding layer configured of a p-type AlGaN semiconductor layer and located above the active layer;
an n-electrode metal layer making Ohmic contact with the n-type cladding layer; and
a first reflective metal layer reflecting ultraviolet light emitted from the active layer,
wherein
the active layer and the p-type cladding layer are formed in a first region on the n-type cladding layer, the first region being in a plane parallel to a surface of the n-type cladding layer,
the n-electrode metal layer is formed on an adjacent region to the first region, the adjacent region being in a second region which is a region other than the first region on the n-type cladding layer,
the first reflective metal layer is formed on a surface of the n-type cladding layer in the second region other than the adjacent region, and
the n-electrode metal layer is arranged between the first region and a region in which the first reflective metal layer contacts the surface of the n-type cladding layer.
2. The nitride semiconductor ultraviolet light-emitting element according to claim 1 , wherein
the first reflective metal layer covers at least part of an upper surface of the n-electrode metal layer, and makes electric contact with the n-electrode metal layer.
3. The nitride semiconductor ultraviolet light-emitting element according to claim 1 , wherein
an AlN molar fraction of the n-type cladding layer is larger than an AlN molar fraction of the active layer, and is 60% or smaller.
4. The nitride semiconductor ultraviolet light-emitting element according to claim 1 , wherein
the first reflective metal layer is configured of Al, or a metal multilayer film or an alloy including Al as a main component.
5. The nitride semiconductor ultraviolet light-emitting element according claim 1 , wherein
a p-type contact layer configured of a p-type AlGaN semiconductor layer that absorbs the ultraviolet light is formed on the p-type cladding layer,
the p-type contact layer includes an opening portion that penetrates to a surface of the p-type cladding layer,
a p-electrode metal layer that makes Ohmic contact or non-rectifying contact with the p-type contact layer is formed on the p-type contact layer so as not to completely cover the opening portion,
a second reflective metal layer that reflects the ultraviolet light is formed at least on the opening portion, and
the second reflective metal layer covers the surface of the p-type cladding layer exposed through the opening portion either directly or through a transparent insulating layer that allows the ultraviolet light to pass therethrough.
6. The nitride semiconductor ultraviolet light-emitting element according to claim 5 , wherein
an AlN molar fraction of the p-type contact layer is 0% or larger and smaller than 10%.
7. The nitride semiconductor ultraviolet light-emitting element according to claim 5 ,
wherein the second reflective metal layer is formed at least on the opening portion and the p-electrode metal layer.
8. The nitride semiconductor ultraviolet light-emitting element according to claim 5 , wherein
the second reflective metal layer is configured of Al, or a metal multilayer film or an alloy including Al as a main component.
9. The nitride semiconductor ultraviolet light-emitting element according to claim 5 , wherein
a ratio of an area of the opening portion to a total area of the p-type contact layer and the opening portion is 66% or more.
10. A nitride semiconductor ultraviolet light-emitting element comprising:
an n-type cladding layer configured of an n-type AlGaN semiconductor layer;
an active layer including an AlGaN semiconductor layer having a band gap energy of 3.4 eV or higher;
a p-type cladding layer configured of a p-type AlGaN semiconductor layer and located above the active layer;
an n-electrode metal layer making Ohmic contact with the n-type cladding layer; and
a first reflective metal layer reflecting ultraviolet light emitted from the active layer,
wherein
the active layer and the p-type cladding layer are formed in a first region on the n-type cladding layer, the first region being in a plane parallel to a surface of the n-type cladding layer,
the n-electrode metal layer is formed on an adjacent region to the first region, the adjacent region being in a second region which is a region other than the first region on the n-type cladding layer,
the first reflective metal layer is formed on a surface of the n-type cladding layer in the second region other than the adjacent region,
the n-electrode metal layer is arranged between the first region and a region in which the first reflective metal layer contacts the surface of the n-type cladding layer;
a p-type contact layer configured of a p-type AlGaN semiconductor layer that absorbs the ultraviolet light is formed on the p-type cladding layer,
the p-type contact layer includes an opening portion that penetrates to a surface of the p-type cladding layer,
a p-electrode metal layer that makes Ohmic contact or non-rectifying contact with the p-type contact layer is formed on the p-type contact layer so as not to completely cover the opening portion,
a second reflective metal layer that reflects the ultraviolet light is formed at least on the opening portion, and
the second reflective metal layer covers the surface of the p-type cladding layer exposed through the opening portion either directly or through a transparent insulating layer that allows the ultraviolet light to pass therethrough.
11. The nitride semiconductor ultraviolet light-emitting element according to claim 10 , wherein
an AlN molar fraction of the p-type contact layer is 0% or larger and smaller than 10%.
12. The nitride semiconductor ultraviolet light-emitting element according to claim 10 , wherein
the second reflective metal layer is formed at least on the opening portion and the p-electrode metal layer.
13. The nitride semiconductor ultraviolet light-emitting element according to claim 10 , wherein
the second reflective metal layer is configured of Al, or a metal multilayer film or an alloy including Al as a main component.
14. The nitride semiconductor ultraviolet light-emitting element according to claim 10 , wherein
a ratio of an area of the opening portion to a total area of the p-type contact layer and the opening portion is 66% or more.
15. The nitride semiconductor ultraviolet light-emitting element according to claim 10 , wherein
the first reflective metal layer covers at least part of an upper surface of the n-electrode metal layer, and makes electric contact with the n-electrode metal layer.
16. The nitride semiconductor ultraviolet light-emitting element according to claim 10 , wherein
an AlN molar fraction of the n-type cladding layer is larger than an AlN molar fraction of the active layer, and is 60% or smaller.
17. The nitride semiconductor ultraviolet light-emitting element according to claim 10 , wherein
the first reflective metal layer is configured of Al, or a metal multilayer film or an alloy including Al as a main component.