Nitride semiconductor light emitting device

Abstract

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.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects, features and other advantages of the present invention will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, in which:

FIG. 1 is a cross-sectional view of a conventional nitride semiconductor light emitting device;

FIG. 2 is a cross-sectional view of a nitride semiconductor light emitting device according to one aspect of the present invention;

FIG. 3 is a cross-sectional view of a nitride semiconductor light emitting device according to another aspect of the present invention;

FIG. 4 is a partially cross-sectional view of a multilayered intermediate layer according to a first embodiment of the present invention;

FIG. 5 is a graph depicting one example of a band-gap profile of the multilayered intermediate layer of FIG. 4;

FIG. 6 is a partially cross-sectional view of a multilayered intermediate layer according to a second embodiment of the present invention;

FIG. 7 is a graph depicting one example of a band-gap profile of the multilayered intermediate layer of FIG. 6;

FIG. 8 is a partially cross-sectional view of a multilayered intermediate layer according to a third embodiment of the present invention;

FIG. 9 is a graph depicting one example of a band-gap profile of the multilayered intermediate layer of FIG. 8; and

FIG. 10 is a graph depicting one example of a band-gap profile of a multilayered intermediate layer according to a fourth embodiment of the present invention.

Claims

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; andat 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 three or more layers having different band-gaps.

2. The light emitting device according to claim 1, wherein the intermediate layer comprises a semiconductor material having the formula InxAlyGa(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˜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 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.

10. The light emitting device according to claim 1, wherein at least a portion of the intermediate layer is doped with n-type impurities

11. The light emitting device according to claim 1, wherein at least a portion of the intermediate layer is doped with p-type impurities.

12. The light emitting device according to claim 1, wherein the intermediate layer is an undoped layer.

13. The light emitting device according to claim 1, wherein In is added as impurities to at least a portion of the intermediate layer.

14. 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.

15. The light emitting device according to claim 14, wherein, among the layers constituting the intermediate layer, one 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.

16. 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.

17. The light emitting device according to claim 1, further comprising: an undoped GaN layer between the substrate and the intermediate layer.

18. The light emitting device according to claim 17, further comprising: a buffer layer between the substrate and the undoped GaN layer.

19. 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.

20. A nitride semiconductor light emitting device, comprising: a first n-type nitride semiconductor layer, an layer, an active layer and a p-type nitride semiconductor layer sequentially formed on a substrate; andan n-side electrode formed on a portion of an upper surface of the second n-type nitride semiconductor layer,wherein the intermediate layer has a multilayer structure formed by stacking three or more layers having different band-gaps, and is positioned below the n-side electrode.

21. The light emitting device according to claim 20, wherein the intermediate layer has a super lattice structure in which laminates of InGaN/GaN/AlGaN layers are repetitiously stacked.

22. The light emitting device according to claim 20, wherein the intermediate layer has a super lattice structure in which laminates of AlGaN/GaN/InGaN layers are repetitiously stacked.