Nitride semiconductor light emitting device
View Patent ↗Disclosed herein is a nitride semiconductor light emitting device, which is improved in luminance and reliability. The light emitting device, comprises an n-type nitride semiconductor layer, an active layer and a p-type nitride semiconductor layer sequentially formed on a substrate, an n-side electrode formed on a portion of an upper surface of the n-type nitride semiconductor layer, and at least one intermediate layer formed between the substrate and the n-type nitride semiconductor layer. The intermediate layer has a multilayer structure of three or more layers having different band-gaps, and is positioned below the n-side electrode.
1. A nitride semiconductor light emitting device, comprising:
an n-type nitride semiconductor layer, an active layer and a p-type nitride semiconductor layer sequentially formed on a substrate;
an n-side electrode formed on a portion of an upper surface of the n-type nitride semiconductor layer; and
at least one intermediate layer formed between the substrate and the n-type nitride semiconductor layer below the n-side electrode,
wherein the intermediate layer having a multilayer structure of three or more layers having different band-gaps and the three or more layer are stacked such that band-gaps of the layers sequentially increase or decrease in a stacking direction.
2. The light emitting device according to claim 1 , wherein the intermediate layer comprises a semiconductor material having the formula In x Al y Ga (1-x-y) N (where 0≦x≦1, 0≦y≦1, 0≦x+y≦1), and the multilayer structure of the intermediate layer has different energy bands with different composition ratios of Al and In.
3. The light emitting device according to claim 1 , wherein each of the layers constituting the intermediate layer has a thickness in the range of 10 to 300 Å.
4. The light emitting device according to claim 1 , wherein the intermediate layer has a super lattice structure.
5. The light emitting device according to claim 1 , wherein the intermediate layer comprises a laminate of AlGaN/GaN/InGaN layers.
6. The light emitting device according to claim 5 , wherein the intermediate layer has the multilayer structure in which laminates of AlGaN/GaN/InGaN layers are repetitiously stacked.
7. The light emitting device according to claim 1 , wherein the intermediate layer comprises a laminate of InGaN/GaN/AlGaN layers.
8. The light emitting device according to claim 7 , wherein the intermediate layer has the multilayer structure in which laminates of InGaN/GaN/AlGaN layers are repetitiously stacked.
9. The light emitting device according to claim 1 , wherein at least a portion of the intermediate layer is doped with n-type impurities.
10. The light emitting device according to claim 1 , wherein at least a portion of the intermediate layer is doped with p-type impurities.
11. The light emitting device according to claim 1 , wherein the intermediate layer is an undoped layer.
12. The light emitting device according to claim 1 , wherein In is added as impurities to at least a portion of the intermediate layer.
13. The light emitting device according to claim 1 , wherein the intermediate layer has the multilayer structure comprising four or more layers of different band-gaps stacked therein.
14. The light emitting device according to claim 1 , wherein the substrate is formed of a material selected from the group consisting of sapphire, SiC, Si, ZnO, MgO and GaN.
15. The light emitting device according to claim 1 , further comprising an undoped GaN layer between the substrate and the intermediate layer.
16. The light emitting device according to claim 15 , further comprising a buffer layer between the substrate and the undoped GaN layer.
17. The light emitting device according to claim 1 , further comprising a current spreading layer between the n-type nitride semiconductor layer and the active layer.
18. A nitride semiconductor light emitting device, comprising:
an n-type nitride semiconductor layer, an active layer and a p-type nitride semiconductor layer sequentially formed on a substrate;
an n-side electrode formed on a portion of an upper surface of the n-type nitride semiconductor layer; and
at least one intermediate layer formed between the substrate and the n-type nitride semiconductor layer below the n-side electrode,
wherein the intermediate layer has the multilayer structure in which laminates of AlGaN/GaN/InGaN/GaN layers are repetitiously stacked, the AlGaN/GaN/InGaN/GaN layers constituting one stacking cycle in the multilayer structure.
19. A nitride semiconductor light emitting device, comprising:
an n-type nitride semiconductor layer, an active layer and a p-type nitride semiconductor layer sequentially formed on a substrate;
an n-side electrode formed on a portion of an upper surface of the n-type nitride semiconductor layer; and
at least one intermediate layer formed between the substrate and the n-type nitride semiconductor layer below the n-side electrode, the intermediate layer having a multilayer structure of four or more layers having different band-gaps,
wherein, among the layers constituting the intermediate layer, two or more layers are stacked between a first layer having the highest band-gap and a second layer having the lowest band-gap such that band-gaps of the layers sequentially increase or decrease in a stacking direction between the first layer and the second layers.