Semiconductor light emitting device with protrusions to improve external efficiency and crystal growth

• US 7,683,386 B2
• Filed: 08/18/2004
• Issued: 03/23/2010
• Est. Priority Date: 08/19/2003
• Status: Active Grant

• Current Assignee: Nichia Corporation
• Original Assignee: Nichia Corporation
• Inventors: Shibutani, Yuuki, Tanaka, Hisanori, Hosokawa, Yasunobu
• Primary Examiner(s): Fahmy; Wael
• Assistant Examiner(s): Ingham; John C
• Application Number:
  US10/920,419
• Publication Number:
  US 20050179130A1
• Time in Patent Office: 2,043 Days
• Field of Search: 257/88, 257/E21.119, 257/94, 257/95, 257/89, 438/29
• US Class Current: 257/88
• CPC Class Codes: H01L 21/0237 Materials
• CPC Class Codes: H01L 21/0242 Crystalline insulating materials
• CPC Class Codes: H01L 21/0243 Surface structure
• CPC Class Codes: H01L 21/02433 Crystal orientation
• CPC Class Codes: H01L 21/0254 Nitrides
• CPC Class Codes: H01L 21/02647 Lateral overgrowth
• CPC Class Codes: H01L 21/02658 Pretreatments cleaning in general H01L21/02041
• CPC Class Codes: H01L 2224/48095 Kinked
• CPC Class Codes: H01L 2224/48247 connecting the wire to a bond pad of the item
• CPC Class Codes: H01L 2224/48465 the other connecting portion not on the bonding area being a wedge bond, i.e. ball-to-wedge, regular stitch
• CPC Class Codes: H01L 2224/49107 on the semiconductor or solid-state body
• CPC Class Codes: H01L 25/167 comprising optoelectronic devices, e.g. LED, photodiodes
• 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 2924/00012 Relevant to the scope of the group, the symbol of which is combined with the symbol of this group
• CPC Class Codes: H01L 2924/13091 Metal-Oxide-Semiconductor Field-Effect Transistor [MOSFET]
• CPC Class Codes: H01L 2924/181 Encapsulation
• CPC Class Codes: H01L 2924/3025 Electromagnetic shielding
• CPC Class Codes: H01L 2933/0083 Periodic patterns for optical field-shaping in or on the semiconductor body or semiconductor body package, e.g. photonic bandgap structures
• CPC Class Codes: H01L 33/007 comprising nitride compounds
• 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 33/38 : with a particular shape

Abstract

A substrate has at least one recess and/or protrusion formed in and/or on a surface thereof so as to scatter or diffract light generated in an active layer. The recess and/or protrusion is formed in such a shape that can reduce crystalline defects in semiconductor layers.

Claims

1. A semiconductor light emitting device comprising:

a transparent substrate including a surface for growing semiconductor layers including an active layer, said surface having protrusions, with a side face of each of said protrusions defining a first inclination angle on a lower portion of said side face and a second inclination angle on an upper portion of said side face, said first inclination angle being greater than said second inclination angle; and

semiconductor layers, of material different from a material of said transparent substrate, on said surface of said transparent substrate, said semiconductor layers covering said protrusions,

wherein either

(i) said upper portion of said side face of each of said protrusions is flat and said lower portion of said side face of each of said protrusions is rough, or

(ii) said upper portion of said side face of each of said protrusions has a surface roughness that is smaller than a surface roughness of said lower portion of said side face of each of said protrusions,

wherein light is reflected at an interface between said protrusions and said semiconductor layers, and

wherein a groove is formed at a bottom periphery of each of said protrusions.

2. The semiconductor device according to claim 1, wherein

said side face of each of said protrusions defines said first inclination angle and said second inclination angle by virtue of comprising two surfaces each having a different inclination angle.

3. The semiconductor device according to claim 2, further comprising:

a buffer layer between said surface of said transparent substrate and said semiconductor layers, said buffer layer having a thickness that is less than a height of said protrusions, said buffer layer having island portions provided on top faces of said protrusions with at least a portion of said side face of each of said protrusions not being covered by said buffer layer, and said buffer layer comprising layer portions provided on said surface of said transparent substrate between said protrusions and separated from said island portions.

4. The semiconductor device according to claim 2, wherein

one of said two surfaces is on a lower side of each of said protrusions and the other of said two surfaces is on an upper side of said each of said protrusions, with the inclination angle of said one of said two surfaces being greater than the inclination angle of said other of said two surfaces.

5. The semiconductor device according to claim 4, wherein

the inclination angle of said one of said two surfaces is larger than 45°

and smaller than 90°

.

6. The semiconductor device according to claim 4, wherein

said material of said transparent substrate is selected from the group consisting of sapphire, SiC and spinel, and

said each of said protrusions has one of a circular, triangular, parallelogram and hexagonal profile in plan view.

7. The semiconductor device according to claim 2, wherein

said protrusions are arranged in a repetitive pattern.

8. The semiconductor device according to claim 1, wherein

said side face of each of said protrusions comprises a curved side face.

9. The semiconductor device according to claim 8, wherein

said side face of each of said protrusions defines said first inclination angle and said second inclination angle by having said curved side face define said first inclination angle on a lower portion of said curved face and said second inclination angle on an upper portion of said curved side face.

10. The semiconductor device according to claim 8, wherein

said curved side face comprises a convexly curved side face.

11. A semiconductor light emitting device comprising:

a transparent substrate including a surface for growing semiconductor layers including an active layer, said surface having protrusions, with a side face of each of said protrusions defining a first inclination angle on a lower portion of said side face and a second inclination angle on an upper portion of said side face, said first inclination angle being greater than said second inclination angle; and

semiconductor layers, of material different from a material of said transparent substrate, on said surface of said transparent substrate, said semiconductor layers covering said protrusions,

wherein said lower portion of said side face of each of said protrusions has notches, said notches being oriented longitudinally, and said upper portion of said side face of each of said protrusions has either no substantial notches or has notches of at least one of a smaller width and a smaller number than a width and a number, respectively, of said notches in said lower portion of said side face of each of said protrusions, and

wherein light is reflected at an interface between said protrusions and said semiconductor layers.

12. The semiconductor device according to claim 11, wherein

said side face of each of said protrusions defines said first inclination angle and said second inclination angle by virtue of comprising two surfaces each having a different inclination angle.

13. The semiconductor device according to claim 12, further comprising:

a buffer layer between said surface of said transparent substrate and said semiconductor layers, said buffer layer having a thickness that is less than a height of said protrusions, said buffer layer having island portions provided on top faces of said protrusions with at least a portion of said side face of each of said protrusions not being covered by said buffer layer, and said buffer layer comprising layer portions provided on said surface of said transparent substrate between said protrusions and separated from said island portions.

14. The semiconductor device according to claim 12, wherein

one of said two surfaces is on a lower side of each of said protrusions and the other of said two surfaces is on an upper side of said each of said protrusions, with the inclination angle of said one of said two surfaces being greater than the inclination angle of said other of said two surfaces.

15. The semiconductor device according to claim 14, wherein

the inclination angle of said one of said two surfaces is larger than 45°

and smaller than 90°

.

16. The semiconductor device according to claim 14, wherein

said material of said transparent substrate is selected from the group consisting of sapphire, SiC and spinel, and

said each of said protrusions has one of a circular, triangular, parallelogram and hexagonal profile in plan view.

17. The semiconductor device according to claim 12, wherein

said protrusions are arranged in a repetitive pattern.

18. The semiconductor device according to claim 11, wherein

said side face of each of said protrusions comprises a curved side face.

19. The semiconductor device according to claim 18, wherein

said side face of each of said protrusions defines said first inclination angle and said second inclination angle by having said curved side face define said first inclination angle on a lower portion of said curved face and said second inclination angle on an upper portion of said curved side face.

20. The semiconductor device according to claim 18, wherein

said curved side face comprises a convexly curved side face.

21. A light emitting device comprising:

a transparent substrate having a surface for growing semiconductor layers including an active layer, said surface having protrusions spaced apart from one another,

a semiconductor light emitting element including semiconductor layers formed on said surface of said transparent substrate, said semiconductor light emitting element covering said protrusions,

wherein a width of a cross section of said protrusions at a base of each of said protrusions is greater than a width of a cross section of each of said protrusions at a top of each of said protrusions, such that

(i) circumscribed by side faces of two closest ones of said protrusions at the bases of these two protrusions is a first circle that is co-planar with said surface of said transparent substrate,

(ii) circumscribed by side faces of at least three adjacent ones of said protrusions at the bases of these at least three protrusions, with two of these at least three protrusions being said two closest ones of said protrusions, is a second circle that is co-planar with said surface of said transparent substrate, and

(iii) circumscribed by the side faces of said two closest ones of said protrusions at the tops of these two protrusions is a third circle that is co-planar with top surfaces of these two protrusions,

with a diameter of said second circle being larger than a diameter of said first circle and smaller than a diameter of said third circle, and with said third circle and said second circle overlapping each other,

wherein an inclination angle of the side face of each of said protrusions is smaller near a top of the protrusion than near a base of the protrusion,

wherein light is reflected at an interface between said protrusions and said semiconductor layers, and

wherein a side face of each of said protrusions has longitudinally-oriented notches.

22. The light emitting device according to claim 21, wherein

said protrusions are disposed periodically.

23. The light emitting device according to claim 22, wherein

said side face of said each of said protrusion comprises a convexly curved side face.

24. The light emitting device according to claim 21, wherein

said base of said each of said protrusions is circular, and said protrusions being disposed periodically includes said protrusions being substantially equally spaced in two axial directions that define an angle of about 60°

.