GaN-BASED SEMICONDUCTOR LIGHT-EMITTING ELEMENT, LIGHT-EMITTING ELEMENT ASSEMBLY, LIGHT-EMITTING APPARATUS, METHOD OF DRIVING GaN-BASED SEMICONDUCTOR LIGHT-EMITTING ELEMENT, AND IMAGE DISPLAY APPARATUS

• US 20090256494A1
• Filed: 03/20/2009
• Published: 10/15/2009
• Est. Priority Date: 04/14/2008
• Status: Active Grant

• Current Assignee: Sony Corporation (Sony Group Corp.)
• Original Assignee: Sony Corporation (Sony Group Corp.)
• Inventors: Naito, Hiroki, Biwa, Goshi, Nishinaka, Ippei
• Granted Patent: US 8,168,986 B2
• Time in Patent Office: Days
• US Class Current: 315/291
• CPC Class Codes: G02F 1/133603 with LEDs
• CPC Class Codes: H01L 2924/00 Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
• CPC Class Codes: H01L 2924/0002 Not covered by any one of groups H01L24/00, H01L24/00 and H01L2224/00
• CPC Class Codes: H01L 33/02 characterised by the semiconductor bodies
• CPC Class Codes: H01L 33/06 within the light emitting region, e.g. quantum confinement structure or tunnel barrier
• CPC Class Codes: H01L 33/32 containing nitrogen

Abstract

A GaN-based semiconductor light-emitting element is provided and includes a first GaN-based compound semiconductor layer; an active layer having a multi-quantum well structure; and a second GaN-based compound semiconductor layer. At least one of barrier layers constituting the active layer is composed of a varying-composition barrier layer, and the composition of the varying-composition barrier layer varies in the thickness direction thereof so that the band-gap energy in a region of the varying-composition barrier layer, the region being adjacent to a boundary between a well layer disposed closer to the second GaN-based compound semiconductor layer and the varying-composition barrier layer, is lower than that in a region of the varying-composition barrier layer, the region being adjacent to a boundary between a well layer disposed closer to the first GaN-based compound semiconductor layer and the varying-composition barrier layer.

Claims

1. A GaN-based semiconductor light-emitting element comprising:

(A) a first GaN-based compound semiconductor layer of n-conductivity type;

(B) an active layer having a multi-quantum well structure including well layers and barrier layers that separate adjacent well layers;

(C) a second GaN-based compound semiconductor layer of p-conductivity type;

(D) a first electrode that is electrically connected to the first GaN-based compound semiconductor layer; and

(E) a second electrode that is electrically connected to the second GaN-based compound semiconductor layer,

wherein at least one of the barrier layers constituting the active layer is composed of a varying-composition barrier layer, and

the composition of the varying-composition barrier layer varies in a thickness direction thereof so that the band-gap energy in a first region of the varying-composition barrier layer, the first region being adjacent to a boundary between a well layer disposed on a side closer to the second GaN-based compound semiconductor layer and the varying-composition barrier layer, is lower than the band-gap energy in a second region of the varying-composition barrier layer, the second region being adjacent to a boundary between a well layer disposed on a side closer to the first GaN-based compound semiconductor layer and the varying-composition barrier layer.

2. The GaN-based semiconductor light-emitting element according to claim 1, wherein the composition of the varying-composition barrier layer varies stepwise in the thickness direction.

3. The GaN-based semiconductor light-emitting element according to claim 2,

wherein the composition of the varying-composition barrier layer varies in the thickness direction in two steps, and

when the boundary between the well layer disposed on the side closer to the first GaN-based compound semiconductor layer and the varying-composition barrier layer is assumed to be a reference, a position to in the thickness direction at which the composition varies satisfies the following relationship:

0.01t_B≦

t₀≦

0.5t_B

wherein t_B represents the thickness of the varying-composition barrier layer.

4. The GaN-based semiconductor light-emitting element according to claim 1, wherein the composition of the varying-composition barrier layer continuously varies in the thickness direction.

5. The GaN-based semiconductor light-emitting element according to claim 1,

wherein the composition of the second region of the varying-composition barrier layer is GaN,

the composition of the first region of the varying-composition barrier layer is In_zGa_(1-z)N, and

the composition of each of the well layers is In_yGa_(1-y)N (wherein y>

z).

6. The GaN-based semiconductor light-emitting element according to claim 5, wherein the relationship 1×

10<sup>−

4</sup>≦

z≦

3×

10<sup>−

2</sup> is satisfied.

7. The GaN-based semiconductor light-emitting element according to claim 1,

wherein the composition of the second region of the varying-composition barrier layer is AlGaN,

the composition of the first region of the varying-composition barrier layer is GaN or In_zGa_(1-z)N, and

the composition of each of the well layers is In_yGa_(1-y)N (wherein y>

z).

8. The GaN-based semiconductor light-emitting element according to claim 1, wherein the number of well layers is in the range of 6 to 15.

9. The GaN-based semiconductor light-emitting element according to claim 8, wherein the number of varying-composition barrier layers is ½

or more of the total number of barrier layers.

10. The GaN-based semiconductor light-emitting element according to Claim 9, wherein the varying-composition barrier layers occupy positions closer to the second GaN-based compound semiconductor layer.

11. The GaN-based semiconductor light-emitting element according to claim 1, wherein the density of a current applied to the active layer is 50 amperes/cm² or more.

12. The GaN-based semiconductor light-emitting element according to claim 1, wherein the active layer has an area in the range of 10⁻

12 to 10<sup>−

8</sup> m².

13. The GaN-based semiconductor light-emitting element according to claim 1, wherein the GaN-based semiconductor light-emitting element has a thickness in the range of 1×

10<sup>−

7</sup> to 1×

10<sup>−

5</sup> m.

14. The GaN-based semiconductor light-emitting element according to claim 1, further comprising:

(F) an impurity diffusion-preventing layer for preventing a p-type impurity from diffusing into the active layer, the impurity diffusion-preventing layer being composed of an undoped GaN-based compound semiconductor, and (G) a laminated structure,

the impurity diffusion-preventing layer and the laminated structure being disposed between the active layer and the second GaN-based compound semiconductor layer in that order from the active layer side,

wherein the laminated structure includes at least one laminate unit in which a GaN-based compound semiconductor layer of p-conductivity type and an undoped GaN-based compound semiconductor layer are laminated in that order from the active layer side.

15. The GaN-based semiconductor light-emitting element according to claim 1, further comprising:

(F) an impurity diffusion-preventing layer for preventing a p-type impurity from diffusing into the active layer, the impurity diffusion-preventing layer being composed of an undoped GaN-based compound semiconductor, and

(G) a third GaN-based compound semiconductor layer of p-conductivity type,

the impurity diffusion-preventing layer and the third GaN-based compound semiconductor layer being disposed between the active layer and the second GaN-based compound semiconductor layer in that order from the active layer side,

wherein at least one undoped GaN-based compound semiconductor layer is provided on a side of the third GaN-based compound semiconductor layer, the side being closer to the second GaN-based compound semiconductor layer.

16. A light-emitting element assembly comprising:

a supporting member; and

a GaN-based semiconductor light-emitting element disposed on the supporting member,

wherein the GaN-based semiconductor light-emitting element includes

(A) a first GaN-based compound semiconductor layer of n-conductivity type;

(B) an active layer having a multi-quantum well structure including well layers and barrier layers that separate adjacent well layers;

(C) a second GaN-based compound semiconductor layer of p-conductivity type;

(D) a first electrode that is electrically connected to the first GaN-based compound semiconductor layer; and

(E) a second electrode that is electrically connected to the second GaN-based compound semiconductor layer,

in which at least one of the barrier layers constituting the active layer is composed of a varying-composition barrier layer, and

the composition of the varying-composition barrier layer varies in a thickness direction thereof so that the band-gap energy in a first region of the varying-composition barrier layer, the first region being adjacent to a boundary between a well layer disposed on a side closer to the second GaN-based compound semiconductor layer and the varying-composition barrier layer, is lower than the band-gap energy in a second region of the varying-composition barrier layer, the second region being adjacent to a boundary between a well layer disposed on a side closer to the first GaN-based compound semiconductor layer and the varying-composition barrier layer.

17. A light-emitting apparatus comprising:

(a) a GaN-based semiconductor light-emitting element; and

(b) a color conversion material that is excited by light emitted from the GaN-based semiconductor light-emitting element to emit light having a wavelength different from the wavelength of the emitted light,

wherein the GaN-based semiconductor light-emitting element includes

(A) a first GaN-based compound semiconductor layer of n-conductivity type;

(B) an active layer having a multi-quantum well structure including well layers and barrier layers that separate adjacent well layers;

(C) a second GaN-based compound semiconductor layer of p-conductivity type;

(D) a first electrode that is electrically connected to the first GaN-based compound semiconductor layer; and

(E) a second electrode that is electrically connected to the second GaN-based compound semiconductor layer,

in which at least one of the barrier layers constituting the active layer is composed of a varying-composition barrier layer, and

the composition of the varying-composition barrier layer varies in a thickness direction thereof so that the band-gap energy in a first region of the varying-composition barrier layer, the first region being adjacent to a boundary between a well layer disposed on a side closer to the second GaN-based compound semiconductor layer and the varying-composition barrier layer, is lower than the band-gap energy in a second region of the varying-composition barrier layer, the second region being adjacent to a boundary between a well layer disposed on a side closer to the first GaN-based compound semiconductor layer and the varying-composition barrier layer.

18. A method of driving a GaN-based semiconductor light-emitting element that includes

(A) a first GaN-based compound semiconductor layer of n-conductivity type;

(B) an active layer having a multi-quantum well structure including well layers and barrier layers that separate adjacent well layers;

(C) a second GaN-based compound semiconductor layer of p-conductivity type;

(D) a first electrode that is electrically connected to the first GaN-based compound semiconductor layer; and

(E) a second electrode that is electrically connected to the second GaN-based compound semiconductor layer,

wherein at least one of the barrier layers constituting the active layer is composed of a varying-composition barrier layer, and

the composition of the varying-composition barrier layer varies in a thickness direction thereof so that the band-gap energy in a first region of the varying-composition barrier layer, the first region being adjacent to a boundary between a well layer disposed on a side closer to the second GaN-based compound semiconductor layer and the varying-composition barrier layer, is lower than the band-gap energy in a second region of the varying-composition barrier layer, the second region being adjacent to a boundary between a well layer disposed on a side closer to the first GaN-based compound semiconductor layer and the varying-composition barrier layer,

the method comprising;

applying a current to the active layer at a current density of 50 amperes/cm² or more.

19. An image display apparatus comprising:

a GaN-based semiconductor light-emitting element for displaying an image,

wherein the GaN-based semiconductor light-emitting element includes

(A) a first GaN-based compound semiconductor layer of n-conductivity type;

(B) an active layer having a multi-quantum well structure including well layers and barrier layers that separate adjacent well layers;

(C) a second GaN-based compound semiconductor layer of p-conductivity type;

(D) a first electrode that is electrically connected to the first GaN-based compound semiconductor layer; and

(E) a second electrode that is electrically connected to the second GaN-based compound semiconductor layer,

in which at least one of the barrier layers constituting the active layer is composed of a varying-composition barrier layer, and

the composition of the varying-composition barrier layer varies in a thickness direction thereof so that the band-gap energy in a first region of the varying-composition barrier layer, the first region being adjacent to a boundary between a well layer disposed on a side closer to the second GaN-based compound semiconductor layer and the varying-composition barrier layer, is lower than the band-gap energy in a second region of the varying-composition barrier layer, the second region being adjacent to a boundary between a well layer disposed on a side closer to the first GaN-based compound semiconductor layer and the varying-composition barrier layer.