Light emitting diode and method for fabricating the same

• US 8,399,944 B2
• Filed: 05/28/2003
• Issued: 03/19/2013
• Est. Priority Date: 09/02/2002
• Status: Expired due to Term

• Current Assignee: Samsung Electronics Co. Ltd.
• Original Assignee: Samsung Electronics Co. Ltd.
• Inventors: Kwak, Joon-seop, Cho, Jae-hee
• Primary Examiner(s): Im, Junghwa M
• Application Number:
  US10/445,992
• Publication Number:
  US 20040041220A1
• Time in Patent Office: 3,583 Days
• Field of Search: 257/89, 257/90, 257/94, 257/96, 257/12, 257/13, 257/14, 257/432, 257/103, 257/79, 257/98, 257/95, 257/E33.061, 257/E33.074, 438/47, 438/979
• US Class Current: 257/432
• CPC Class Codes: H01L 2224/48091 Arched
• CPC Class Codes: H01L 2224/48247 connecting the wire to a bond pad of the item
• CPC Class Codes: H01L 2224/48257 connecting the wire to a die pad of the item
• CPC Class Codes: H01L 2224/8592 Applying permanent coating, e.g. protective coating
• 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 2924/00014 the subject-matter covered by the group, the symbol of which is combined with the symbol of this group, being disclosed without further technical details
• CPC Class Codes: H01L 2924/181 Encapsulation
• CPC Class Codes: H01L 2933/0041 relating to wavelength conversion elements
• CPC Class Codes: H01L 33/007 comprising nitride compounds
• CPC Class Codes: H01L 33/0095 Post-treatment of devices, e.g. annealing, recrystallisation or short-circuit elimination
• CPC Class Codes: H01L 33/20 with a particular shape, e.g. curved or truncated substrate
• 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

A light emitting diode and a method for fabricating the same are provided. The light emitting diode includes: a transparent substrate; a semiconductor material layer formed on the top surface of a substrate with an active layer generating light; and a fluorescent layer formed on the back surface of the substrate with controlled varied thicknesses. The ratio of light whose wavelength is shifted while propagating through the fluorescent layer and the original light generated in the active layer can be controlled by adjusting the thickness of the fluorescent layer, to emit desirable homogeneous white light from the light emitting diode.

Claims

1. A light emitting diode comprising:

a substrate which transmits light, the substrate having a top surface and a back surface opposite the top surface;

a first semiconductor layer, an active layer generating a first light, and a second semiconductor layer disposed, in that order, on the top surface of the substrate,

a fluorescent layer formed on the back surface of the substrate, and converting a portion of the first light to second light having a different wavelength from the first light; and

wherein the substrate has at least one etched hole defined in a portion of the back surface of the substrate, and portions of the back surface of the substrate surrounding the at least one etched hole are planar, and the fluorescent layer fills all the inside of the at least one etched hole,

wherein the fluorescent layer includes at least one relatively thick area and at least one relatively thin area such that the first light is converted into the second light with higher efficiency in the at least one thick area than in the at least one thin area

wherein the at least one relatively thick area of the fluorescent layer is formed in the at least one etched hole and the at least one relatively thin area of the fluorescent layer is formed on the portions of the back surface of the substrate surrounding the at least one etched hole.

2. The light emitting diode of claim 1, wherein the fluorescent layer is formed as dual layers with different patterns.

3. The light emitting diode of claim 1, wherein the substrate is a sapphire substrate.

4. The light emitting diode of claim 1, wherein the semiconductor material layer comprises:

a first compound semiconductor layer deposited on the top surface of the substrate;

the active layer deposited on the top surface of the first compound semiconductor layer; and

a second compound semiconductor layer deposited on the top surface of the active layer.

5. The light emitting diode of claim 4, wherein the first compound semiconductor layer is an n-type doped or undoped GaN-based III-V nitride compound semiconductor layer.

6. The light emitting diode of claim 4, wherein the second compound semiconductor layer is a p-type doped GaN-based III-V nitride compound semiconductor layer.

7. The light emitting diode of claim 4, wherein the active layer is an n-type doped or undoped InAIGaN compound semiconductor layer where 0≦

x≦

1, 0≦

y≦

1, and x+y≦

1.

8. The light emitting diode of claim 1, wherein the second light is yellow light.

9. The light emitting diode of claim 8, wherein the fluorescent layer is formed of a fluorescent material including a garnet fluorescent material activated with cerium containing at least one element selected from the group consisting of yttrium, lutetium, scandium, lanthanum, gadolinium, and samarium, and at least one element selected from the group consisting of aluminum, gallium, and indium.

10. The light emitting diode of claim 1, wherein a difference in thicknesses between the at least one relatively thick area and the at least one thin area is substantially 50 μ

m.

11. The light emitting diode of claim 1, wherein the width of at least one relatively thick area substantially ranges between 250 μ

m and 500 μ

m.

12. The light emitting diode of claim 1, wherein the first light is blue light of a wavelength of 420˜

470 nm, and the second light includes at least one fluorescent material of Y₂O₂S;

Eu³⁺,Bi³⁺, YVO₄;

Eu³⁺,Bi³⁺, SrS;

Eu²⁺, SrY₂S₄;

Eu²⁺, CaLa₂S₄;

Ce³⁺, (Ca, Sr)S;

Eu²⁺ and at least one fluorescent material of YBO₃;

Ce³⁺, Tb³⁺, BaMgAl₁₀O₁₇;

Eu²⁺,Mn²⁺, (Sr, Ba, Ca)(Al, Ga)₂S₄;

Eu²⁺.

13. The light emitting diode of claim 1, wherein the first light is UV light, and the second light includes red, green and blue light.

14. The light emitting diode of claim 1, wherein the first light is blue light of a wavelength of 420˜

470 nm, and the second light is yellow light.

15. The light emitting diode of claim 1, wherein the first light is blue light of a wavelength of 420˜

470 nm, and the second light includes red and green.

16. The light emitting diode of claim 1, wherein the first light is blue light of a wavelength of 420˜

470 nm, and the second light includes red of a wavelength of 610-625 nm and/or green of a wavelength of 530˜

555 nm.

17. The light emitting diode of claim 1, wherein the at least one hole has a sloped sidewall.