Gallium nitride-based compound semiconductor light-emitting device
An object of the present invention is to provide a gallium nitride-based compound semiconductor light-emitting device having a reflective positive electrode configured to achieve excellent light extraction efficiency. The inventive gallium nitride-based compound semiconductor light-emitting device has a gallium nitride-based compound semiconductor layer structure comprising an n-type semiconductor layer, a light-emitting layer and a p-type semiconductor layer, on a substrate, wherein a positive electrode provided on the p-type semiconductor layer is a reflective positive electrode comprising a transparent material layer and a reflective metal layer formed on the transparent material layer.
1. A gallium nitride-based compound semiconductor light-emitting device having a gallium nitride-based compound semiconductor layer structure comprising an n-type semiconductor layer, a light-emitting layer and a p-type semiconductor layer, on a substrate, wherein a positive electrode provided on the p-type semiconductor layer is a reflective positive electrode comprising a transparent material layer and a reflective metal layer formed on the transparent material layer,
wherein the reflective metal layer is formed with depressions/protrusions on a surface thereof that faces the transparent material layer, and
wherein the reflective metal layer covers an entire surface of the transparent material layer.
2. A gallium nitride-based compound semiconductor light-emitting device according to claim 1 , wherein the transparent material layer contains an electrically conductive material.
3. A gallium nitride-based compound semiconductor light-emitting device according to claim 1 , wherein the transparent material layer contains an electrically nonconductive material.
4. A gallium nitride-based compound semiconductor light-emitting device according to claim 2 , wherein the transparent material layer is in contact with the p-type semiconductor layer and functions as a positive electrode contact layer.
5. A gallium nitride-based compound semiconductor light-emitting device according to claim 1 , wherein a positive electrode contact layer is interposed between the transparent material layer and the p-type semiconductor layer.
6. A gallium nitride-based compound semiconductor light-emitting device according to claim 2 , wherein the transparent material layer is formed from at least one material selected from the group consisting of ITO, TiO 2 , ZnO, ZnS, Bi 2 O 3 , MgO, ZnAlO, and SnO 2 .
7. A gallium nitride-based compound semiconductor light-emitting device according to claim 6 , wherein the transparent material layer is formed from at least one material selected from the group consisting of ITO, ZnO, MgO, ZnAlO, and SnO 2 .
8. A gallium nitride-based compound semiconductor light-emitting device according to claim 1 , wherein the reflective metal layer is formed from at least one kind of metal selected from the group consisting of Ag, Al, Fe, Cr, Ti, Co, Ni, Pd, Os, Ru, Pt, Rh, and Ir, or from an alloy containing at least one of these metals.
9. A gallium nitride-based compound semiconductor light-emitting device according to claim 8 , wherein the reflective metal layer is formed from at least one kind of metal selected from the group consisting of Ag, Al, Fe, Pt, Rh, and Ir, or from an alloy containing at least one of these metals.
10. A gallium nitride-based compound semiconductor light-emitting device according to claim 9 , wherein the reflective metal layer is formed from at least one kind of metal selected between Ag and Al, or from an alloy containing at least either one of these metals.
11. A gallium nitride-based compound semiconductor light-emitting device according to claim 1 , wherein the transparent material layer is formed with depressions/protrusions on a surface thereof that faces the reflective metal layer.
12. A gallium nitride-based compound semiconductor light-emitting device according to claim 1 , wherein the depressions/protrusions are formed in a stripe pattern.
13. A gallium nitride-based compound semiconductor light-emitting device according to claim 1 , wherein the depressions/protrusions are formed in a dot-like or lattice-like pattern.
14. A gallium nitride-based compound semiconductor light-emitting device according to claim 1 , wherein the depressions/protrusions are formed in random shapes.
15. A gallium nitride-based compound semiconductor light-emitting device according to claim 1 , wherein the depressions/protrusions are formed from curved surface.
16. A gallium nitride-based compound semiconductor light-emitting device according to claim 1 , wherein the depressions/protrusions are formed from plane surface slanted relative to a substrate surface.
17. A gallium nitride-based compound semiconductor light-emitting device according to claim 16 , wherein the slanted plane surface makes angles of 5 to 85 degrees relative to the substrate surface.
18. A gallium nitride-based compound semiconductor light-emitting device according to claim 1 , wherein the depressions/protrusions have height differences of 0.01 μm to 10 μm.
19. A lamp comprising a gallium nitride-based compound semiconductor light-emitting device according to claim 1 .