LED sapphire substrate with groups of three projections on the surface

• US 9,070,814 B2
• Filed: 06/25/2014
• Issued: 06/30/2015
• Est. Priority Date: 08/06/2010
• Status: Active Grant

• Current Assignee: Nichia Corporation
• Original Assignee: Nichia Corporation
• Inventors: Narita, Junya, Okada, Takuya, Wakai, Yohei, Inoue, Yoshiki, Sako, Naoya, Kadan, Katsuyoshi
• Primary Examiner(s): Bradford, Peter
• Application Number:
  US14/314,516
• Publication Number:
  US 20140306265A1
• Time in Patent Office: 370 Days
• Field of Search: 257/E33.074, 257/E33.067, 257/E51.021, 257/98
• US Class Current: 1/1
• CPC Class Codes: H01L 21/0242 Crystalline insulating materials
• CPC Class Codes: H01L 21/0243 Surface structure
• CPC Class Codes: H01L 21/02458 Nitrides
• CPC Class Codes: H01L 21/0254 Nitrides
• CPC Class Codes: H01L 33/007 comprising nitride compounds
• CPC Class Codes: H01L 33/10 with a light reflecting structure, e.g. semiconductor Bragg reflector
• CPC Class Codes: H01L 33/20 with a particular shape, e.g. curved or truncated substrate
• CPC Class Codes: H01L 33/22 Roughened surfaces, e.g. at the interface between epitaxial layers
• CPC Class Codes: H01L 33/32 containing nitrogen
• CPC Class Codes: Y10T 428/24 Structurally defined web or sheet [e.g., overall dimension, etc.]
• CPC Class Codes: Y10T 428/24479 including variation in thickness

Abstract

The sapphire substrate has a principal surface for growing a nitride semiconductor to form a nitride semiconductor light emitting device and comprising a plurality of projections of the principal surface, wherein an outer periphery of a bottom surface of each of the projections has at least one depression. This depression is in the horizontal direction. The plurality of projections are arranged so that a straight line passes through the inside of at least any one of projections when the straight line is drawn at any position in any direction in a plane including the bottom surfaces of the plurality of projections.

Claims

1. A sapphire substrate having a principle surface for growing a nitride semiconductor to form a nitride semiconductor light emitting device, the sapphire substrate comprising:

a plurality of groupings of projections, each grouping including exactly three sub-groupings, each sub-grouping being discontinuous from each other sub-grouping, the plurality of sub-groupings including;

a first sub-grouping on a first side of the grouping, the first sub-grouping comprising a first projection,

a second sub-grouping on a second side of the grouping, the second sub-grouping comprising a second projection, and

a third sub-grouping on a third side of the grouping, the third sub-grouping comprising a third projection,

wherein each of the first, second, and third projections has a width, and a length that is greater than the width,

wherein the first projection extends lengthwise in a first direction,

wherein the second projection extends lengthwise in a second direction that is different from the first direction, and

wherein the third projection extends lengthwise in a third direction that is different from the first and second directions.

2. The sapphire substrate according to claim 1, wherein each sub-grouping includes exactly one projection.

3. The sapphire substrate according to claim 1, wherein each projection has a petal shape.

4. The sapphire substrate according to claim 3, wherein each petal-shaped projection includes a vertex that faces away from a center of a grouping of which said petal-shaped projection is a part.

5. The sapphire substrate according to claim 3, wherein each petal-shaped projection includes a vertex that faces toward a center of a grouping of which said petal-shaped projection is a part.

6. The sapphire substrate according to claim 1, wherein the first, second, and third directions of the projections in said first, second, and third sub-groupings are directions extending from a center of a grouping of which said projections are a part.

7. The sapphire substrate according to claim 1, wherein the first, second, and third directions are within a range of ±

10 degrees of directions rotated clockwise by 30 degrees from crystal axes “

a”

of the sapphire substrate.

8. The sapphire substrate according to claim 1, wherein the first, second, and third directions are within a range of ±

10 degrees of directions rotated counter-clockwise by 30 degrees from crystal axes “

a”

of the sapphire substrate.

9. The sapphire substrate according to claim 1,

wherein each projection has a petal shape,

wherein each petal-shaped projection includes a vertex that faces away from a center of a grouping of which said petal-shaped projection is a part, and

wherein the first, second, and third directions are within a range of ±

10 degrees of directions rotated counter-clockwise by 30 degrees from crystal axes “

a”

of the sapphire substrate.

10. The sapphire substrate according to claim 1,

wherein each projection has a petal shape,

wherein each petal-shaped projection includes a vertex that faces toward a center of a grouping of which said petal-shaped projection is a part, and

wherein the first, second, and third directions are within a range of ±

10 degrees of directions rotated clockwise by 30 degrees from crystal axes “

a”

of the sapphire substrate.

11. The sapphire substrate according to claim 1, wherein the plurality of projections are arranged so that any straight line that is drawn at any position in any direction in a plane including the bottoms of the projections passes through a geometric area of the bottom of at least one of projections.

12. The sapphire substrate according to claim 1, wherein each of the projections has a top surface that has a shape substantially similar to that of its bottom.

13. The sapphire substrate according to claim 1, wherein the plurality of groupings are arranged so as to form a plurality of rows, and wherein the projections are arranged so that bisectors that bisect angles of vertexes of projections arranged in the same row are located on a straight line.

14. The sapphire substrate according to claim 1, wherein each petal-shaped projection includes a vertex that faces away from a center of a grouping of which said petal-shaped projection is a part, and a rounded end that faces toward a center of said grouping.

15. The sapphire substrate according to claim 1, wherein each petal-shaped projection includes a vertex that faces toward a center of a grouping of which said petal-shaped projection is a part, and a rounded end that faces away from a center of said grouping.

16. A nitride semiconductor light emitting device formed by growing a nitride semiconductor on the principal surface of the sapphire substrate according to claim 1.