Nitride semiconductor light emitting device

• US 7,470,938 B2
• Filed: 11/09/2004
• Issued: 12/30/2008
• Est. Priority Date: 03/30/2004
• Status: Active Grant

• Current Assignee: Samsung Electronics Co. Ltd.
• Original Assignee: Samsung Electro-Mechanics Co., Ltd. (Samsung Group)
• Inventors: Kim, Yong Chun, Lee, Jeong Wook, Lee, Jae Hoon, Kim, Hyun Kyung
• Primary Examiner(s): Soward; Ida M
• Application Number:
  US10/983,637
• Publication Number:
  US 20050221521A1
• Time in Patent Office: 1,512 Days
• Field of Search: 257/13, 257 79-103, 257/918, 438 29- 32
• US Class Current: 257/103
• CPC Class Codes: H01L 33/007 comprising nitride compounds
• 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: Y10S 257/918 Light emitting regenerative switching device, e.g. light emitting scr arrays, circuitry

Abstract

In a nitride semiconductor light emitting device having patterns formed on the upper and lower surfaces of a substrate from which light is emitted in a flip chip bonding structure, the patterns are capable of changing light inclination at the upper and lower surfaces of the substrate to decrease total reflection at the interfaces, thereby improving light emitting efficiency. The device includes a substrate having upper and lower surfaces on which predetermined patterns are formed such that light can be incident within a critical angle, the substrate allowing a gallium nitride-based semiconductor material to be grown thereon, an n-type nitride semiconductor layer formed on the upper surface of the substrate, an active layer formed on the upper surface of the n-type nitride semiconductor layer such that the n-type nitride semiconductor layer is partially exposed, a p-type nitride semiconductor layer formed on the upper surface of the active layer, a p-electrode formed on the upper surface of the p-type nitride semiconductor layer, and an n-side electrode formed on the partially exposed n-type nitride semiconductor layer.

Claims

1. A nitride semiconductor light emitting device comprising:

a substrate having upper and lower surfaces;

a n-type nitride semiconductor layer formed on the upper surface of the substrate;

an active layer formed on the upper surface of the n-type nitride semiconductor layer such that the n-type nitride semiconductor layer is partially exposed;

a p-type nitride semiconductor layer formed on the upper surface of the active layer;

a p-electrode formed on an upper surface of the p-type nitride semiconductor layer; and

a n-side electrode formed on the partially exposed n-type nitride semiconductor layer;

wherein the lower surface of the substrate comprises a regular pattern of hemispherical cavities for reducing total internal reflection at an interface between said lower surface of the substrate and an environment outside said device; and

wherein the upper surface of the substrate comprises a regular pattern of hemispherical raised projections for reducing total internal reflection at an interface between said upper surface of the substrate and the n-type nitride semiconductor layer formed thereon.

2. The device as set forth in claim 1, wherein said upper surface of the substrate is a continuous plane, which completely surrounds all said raised projections or cavities.

3. The device as set forth in claim 1, wherein said lower surface of the substrate is a continuous plane, which completely surrounds all said raised projections or cavities.

4. A nitride semiconductor light emitting device comprising:

a substrate having upper and lower surfaces;

a n-type nitride semiconductor layer formed on the upper surface of the substrate;

an active layer formed on the upper surface of the n-type nitride semiconductor layer such that the n-type nitride semiconductor layer is partially exposed;

a p-type nitride semiconductor layer formed on the upper surface of the active layer;

a p-electrode formed on an upper surface of the p-type nitride semiconductor layer;

a n-side electrode formed on the partially exposed n-type nitride semiconductor layer; and

wherein the lower surface of the substrate comprises a plurality of raised projections or cavities of a predetermined shape for changing light inclination at the lower surface of the substrate to reduce total internal reflection at an interface between said lower surface of the substrate and an environment outside said device; and

wherein the upper surface of the substrate comprises a plurality of raised projections or cavities of a predetermined shape for changing light inclination at the upper surface of the substrate to reduce total internal reflection at an interface between said upper surface of the substrate and the n-type nitride semiconductor layer formed thereon.

5. The device as set forth in claim 4, wherein said raised projections are hemispherical in shape.

6. The device as set forth in claim 4, wherein said cavities are hemispherical in shape.

7. The device as set forth in claim 4, wherein said raised projections are parallel prism-shaped stripes.

8. The device as set forth in claim 4, wherein said cavities are parallel prism-shaped stripes.

9. The device as set forth in claim 4, wherein said raised projections or cavities are uniformly arranged at regular interval.

10. The device as set forth in claim 4, wherein said upper surface of the substrate is a continuous plane, which completely surrounds all said raised projections or cavities.

11. The device as set forth in claim 4, wherein said lower surface of the substrate is a continuous plane, which completely surrounds all said raised projections or cavities.

12. The device as set forth in claim 4, wherein said predetermined shape satisfies the following equation:

α

₀=sin<sup>−

1</sup>(n₂/n₁);

where α

₀ is the minimum value of the incident angle where total reflection of light occurs;

n₁ is the light refractive index of said n-type nitride semiconductor layer; and

n₂ is the light refractive index of said substrate.