Semiconductor light emitting device and its manufacturing method

• US 20030062530A1
• Filed: 10/25/2002
• Published: 04/03/2003
• Est. Priority Date: 12/24/1998
• Status: Active Grant

• Current Assignee: Samsung Electronics Co. Ltd.
• Original Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Inventors: Okazaki, Haruhiko, Nitta, Koichi, Nozaki, Chiharu
• Granted Patent: US 6,924,163 B2
• Time in Patent Office: Days
• US Class Current: 257/79
• CPC Class Codes: H01L 21/42 Bombardment with radiation
• CPC Class Codes: H01L 2933/0016 relating to electrodes
• 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: H01L 33/382 the electrode extending partially in or entirely through the semiconductor body
• CPC Class Codes: H01L 33/42 Transparent materials
• CPC Class Codes: H01L 33/508 having a non-uniform spatial arrangement or non-uniform concentration, e.g. patterned wavelength conversion layer, wavelength conversion layer with a concentration gradient of the wavelength conversion material

Abstract

Efficiency of leading out light released from an active layer, i.e. the external quantum efficiency, can be improved remarkably by processing a light lead-out surface to have an embossment. A layer containing a p-type dopant like magnesium (Mg) is deposited near the surface of a p-type GaN layer to diffuse it there, and a p-side electrode is made on the p-type GaN layer after removing the deposited layer. This results in ensuring ohmic contact with the p-side electrode, preventing exfoliation of the electrode and improving the reliability.

Claims

1. A semiconductor light emitting device comprising:

a light emitting portion made of a nitride compound semiconductor, and

a light lead-out surface on which an embossment is formed to improve the external quantum efficiency of light emitted from said light emitting portion.

2. The semiconductor light emitting device according to claim 1 further comprising a nitride compound semiconductor layer;

and a transparent electrode,

said embossment being formed on one surface of said nitride compound semiconductor layer, and said transparent electrode being formed on said one surface of said nitride compound semiconductor layer.

3. The semiconductor light emitting device according to claim 2 wherein said nitride compound semiconductor layer under said transparent electrode contains a p-type dopant with a high concentration near the interface to said transparent electrode layer.

4. The semiconductor light emitting device according to claim 2 wherein said transparent electrode includes a layer of a metal having a thickness not thicker than 100 nm and formed in contact with said nitride compound semiconductor.

5. The semiconductor light emitting device according to claim 4 wherein said metal contains at least one of nickel (Ni) and platinum (Pt).

6. The semiconductor light emitting device according to claim 1 wherein said embossment includes a plurality of cylindrical lens-shaped convex portions.

7. The semiconductor light emitting device according to claim 1 wherein said embossment includes a hemispherical convex portion.

8. The semiconductor light emitting device according to claim 1 further comprising a nitride compound semiconductor layer having an even surface;

and a transparent electrode formed on said nitride compound semiconductor layer,

said embossment being formed on a surface of said transparent electrode.

9. The semiconductor light emitting device according to claim 1 further comprising:

a nitride compound semiconductor layer having an even surface;

a transparent electrode formed on said even surface of said nitride compound semiconductor layer; and

a light lead-out layer formed on said transparent electrode and having a transparency,

said embossment being formed on a surface of said light lead-out layer.

10. The semiconductor light emitting device according to claim 9 wherein said light lead-out layer is made of an organic material or an inorganic material.

11. The semiconductor light emitting device according to claim 9 wherein said light lead-out layer includes a fluorescent material which absorbs a primary light emitted from said light emitting portion and releases a secondary light having a different wavelength from said primary light.

12. The semiconductor light emitting device according to claim 1 further comprising a substrate made of a material other than nitride compound semiconductor,

said light emitting portion being provided on one side of said substrate, and said embossment being provided on another side of said substrate.

13. The semiconductor light emitting device according to claim 12 further comprising a reflector reflecting a light emitted from said light emitting portion to release said light outside through said substrate,

said reflector also serving as an electrode injecting a current into said light emitting portion.

14. The semiconductor light emitting device according to claim 1 further comprising a substrate made of nitride compound semiconductor,

said light emitting portion being provided on one side of said substrate, and said embossment being provided on another side of said substrate.

15. The semiconductor light emitting device according to claim 14 further comprising a reflector reflecting a light emitted from said light emitting portion to release said light outside through said substrate,

said reflector also serving as an electrode injecting a current into said light emitting portion.

16. A semiconductor light emitting device comprising:

a light emitting portion made of a nitride compound semiconductor, and

a reflector reflecting a light emitted from said light emitting portion at a reflecting interface to release said light outside,

wherein an embossment is formed on said reflecting interface.

17. The semiconductor light emitting device according to claim 16 wherein said reflector also serves as an electrode.

18. A semiconductor light emitting device comprising:

a substrate;

a mesa provided on one side of said substrate and including

a light emitting portion;

a reflector provided on said mesa and reflecting a light emitted from said light emitting portion to release said light outside through said substrate;

a light-transmissive portion provided on a side surface of said mesa;

a reflective layer coated on a surface of said light-transmissive portion; and

an embossment provided on another side of said substrate to improve the external quantum efficiency of lights emitted from said light emitting portion,

said reflective layer reflecting a light leaking sideward from said light emitting portion of said mesa so as to release the light outside through said substrate.

19. A manufacturing method of a semiconductor light emitting device comprising the steps of:

forming a nitride compound semiconductor having a light emitting portion;

depositing on a surface of said nitride compound semiconductor a doping metal layer containing a dopant for increasing electric conductivity of said nitride compound semiconductor;

diffusing said dopant into said nitride compound semiconductor;

removing said doping metal layer from the surface of said nitride compound semiconductor; and

forming an electrode on the surface of said nitride compound semiconductor.

20. The manufacturing method of a semiconductor light emitting device according to claim 19 further comprising a step of forming an embossment on the surface of said nitride compound semiconductor prior to the step of depositing said doping metal layer,

said electrode being transparent to light released from said light emitting portion.

21. The manufacturing method of a semiconductor light emitting device according to claim 19 wherein said doping metal layer includes a first layer stacked on the surface of said nitride compound semiconductor and containing said dopant, and a second layer as a cap layer stacked on said first layer.

22. The manufacturing method of a semiconductor light emitting device according to claim 21 wherein said first layer includes magnesium (Mg) as the dopant, and said second layer is formed of gold (Au).

23. The manufacturing method of a semiconductor light emitting device according to claim 19 further comprising a step of depositing a contact metal layer transparent to a light emitted from said light emitting portion on the surface of said nitride compound semiconductor between the step of removing said doping metal layer and the step of forming said electrode.

24. The manufacturing method of a semiconductor light emitting device according to claim 23 wherein said contact metal layer contains at least one of nickel (Ni) and platinum (Pt), and has a thickness not thicker than 100 nm.