Light Emitting Devices with Improved Light Extraction Efficiency

• US 20080023719A1
• Filed: 10/08/2007
• Published: 01/31/2008
• Est. Priority Date: 09/12/2000
• Status: Active Grant

• Current Assignee: Lumileds LLC (Apollo Global Management, Inc.)
• Original Assignee: Philips Lumileds Lighting Company LLC (Apollo Global Management, Inc.)
• Inventors: Snyder, Wayne, Lowery, Christopher, Taber, Robert, Krames, Michael, Hofler, Gloria, Trottier, Troy, Mueller, Gerd, Uebbing, John, Mueller-Mach, Regina, Pocius, Douglas, Steranka, Frank, Camras, Michael
• Granted Patent: US 8,049,234 B2
• Time in Patent Office: Days
• US Class Current: 257/98
• CPC Class Codes: H01L 33/20 with a particular shape, e.g. curved or truncated substrate
• CPC Class Codes: H01L 33/32 containing nitrogen
• CPC Class Codes: H01L 33/405 Reflective materials
• CPC Class Codes: H01L 33/502 Wavelength conversion materials
• CPC Class Codes: H01L 33/58 Optical field-shaping elements
• CPC Class Codes: H01L 33/62 Arrangements for conducting electric current to or from the semiconductor body, e.g. lead-frames, wire-bonds or solder balls

Abstract

Light emitting devices with improved light extraction efficiency are provided. The light emitting devices have a stack of layers including semiconductor layers comprising an active region. The stack is bonded to a transparent optical element.

Claims

1. A structure comprising:

an LED die comprising an active region disposed between a semiconductor layer of n-type conductivity and a semiconductor layer of p-type conductivity; and

an optical element including a recess in a bottom surface of the optical element;

wherein the LED die is disposed within the recess and bonded to the optical element.

2. The structure of claim 1 further comprising a transparent bonding material disposed between the recess in the optical element and a top surface of the LED die.

3. The structure of claim 1 wherein the LED die is directly bonded to the optical element.

4. The structure of claim 1 wherein a refractive index of the optical element for light emitted by the active region is greater than 1.5.

5. The structure of claim 1 further comprising a luminescent material disposed between the optical element and the LED die.

6. The structure of claim 1 wherein the LED comprises a transparent substrate.

7. The structure of claim 1 further comprising n- and p-type contacts electrically connected to the semiconductor layer of n-type conductivity and a semiconductor layer of p-type conductivity, wherein both the n- and p-type contacts are formed on a bottom surface of the LED die.

8. The structure of claim 1 wherein:

a top surface of the LED die is bonded to a surface of the recess in the optical element; and

at least a portion of the bottom surface of the optical element is below a top surface of the LED die.

9. The structure of claim 1 wherein the optical element comprises a lens.

10. The structure of claim 1 further comprising a luminescent material, wherein at least a portion of the optical element is disposed between the luminescent material and the LED die.

11. A structure comprising:

an LED die comprising an active region disposed between a semiconductor layer of n-type conductivity and a semiconductor layer of p-type conductivity; and

an optical element bonded to the LED die;

wherein the optical element is formed from a material having a thermal expansion coefficient approximately matching a thermal expansion coefficient of the LED die.

12. The structure of claim 11 wherein a refractive index of the optical element for light emitted by the active region is greater than 1.5.

13. The structure of claim 11 further comprising a luminescent material disposed between the optical element and the LED die.

14. A structure comprising:

an LED die comprising an active region disposed between a semiconductor layer of n-type conductivity and a semiconductor layer of p-type conductivity;

an optical element bonded to the LED die; and

a luminescent material disposed between the LED die and the optical element.

15. The structure of claim 14 wherein the luminescent material is disposed in a bonding material, wherein the bonding material is disposed between the LED die and the optical element and bonds the LED die to the optical element.

16. The structure of claim 14 wherein a refractive index of the optical element for light emitted by the active region is greater than 1.5.

17. A structure comprising:

an LED die comprising an active region disposed between a semiconductor layer of n-type conductivity and a semiconductor layer of p-type conductivity;

an optical element comprising a luminescent material bonded to the LED die; and

a bonding material disposed between the LED die and the optical element.

18. A structure comprising:

an LED die comprising an active region disposed between a semiconductor layer of n-type conductivity and a semiconductor layer of p-type conductivity; and

an optical element comprising zinc, the optical element being bonded to the LED die.

19. The structure of claim 18 further comprising a luminescent material disposed in the optical element.

20. The structure of claim 18 wherein the LED die is directly bonded to the optical element.

21. A structure comprising:

an LED die comprising an active region disposed between a semiconductor layer of n-type conductivity and a semiconductor layer of p-type conductivity, the active region comprising at least one group III element and phosphorus;

an optical element; and

a bonding material, disposed between the optical element and the LED die;

wherein at least one of the optical element and the bonding material comprises chalcogenide glass.

22. The structure of claim 21 wherein at least one of the optical element and the bonding material comprises (Ge,Sb,Ga)(S,Se) chalcogenide glass.

23. The structure of claim 21 wherein at least one of the optical element and the bonding material comprise one of a metal fluoride and a metal oxide.

24. A structure comprising:

an LED die comprising an active region disposed between a semiconductor layer of n-type conductivity and a semiconductor layer of p-type conductivity;

a luminescent element bonded to the LED die; and

a bonding material disposed between the LED die and the luminescent element.

25. The structure of claim 24, wherein the luminescent element comprises yttrium aluminum garnet.

26. The structure of claim 24, wherein the luminescent element is one of a lens and an optical concentrator.

27. The structure of claim 24, further comprising an optical element coupled to the luminescent element so that the luminescent element is between the optical element and the bonding material.

28. A method comprising:

mounting a light emitting device die to a submount through at least one contact element; and

bonding an optical element to the light emitting device die after the light emitting device die is mounted to the submount, wherein the bonding of the optical element to the light emitting device die is effected by a bonding layer disposed between the optical element and the light emitting device die.

29. The method of claim 28, wherein the bonding layer comprises an inorganic material.

30. The method of claim 28, wherein bonding comprises elevating a temperature of the optical element, the bonding layer, the light emitting device die, and the submount to a temperature that is less than the melting temperature of the contact element.

31. The method of claim 28, wherein the contact element is on at least one of the bottom surface of the light emitting device die and the top surface of the submount, the contact element providing electrical contact between the light emitting device die and the submount.

32. The method of claim 28, wherein a temperature used to bond the optical element to the light emitting device die is less than approximately 500°

C.

33. The method of claim 28, wherein the bonding layer between the optical element and the light emitting device die comprises a metal oxide.

34. The method of claim 33, wherein the metal oxide is at least one of tungsten oxide, titanium oxide, nickel oxide, titanium oxide, zirconium oxide, indium tin oxide, and chromium oxide.

35. The method of claim 28, further comprising depositing a coating of wavelength converting material on the optical element.

36. The method of claim 28, wherein the optical element includes wavelength converting material.

37. The method of claim 28, wherein the optical element comprises yttrium aluminum garnet.

38. The method of claim 28, wherein the light emitting device die comprises a stack of semiconductor layers, at least one of which is an active region that emits lights, and a first contact and a second contact electrically coupled to apply a voltage across the active region;

the first contact and the second contact disposed on a same side of the stack.

39. A method comprising:

providing a semiconductor light emitting device comprising a stack of semiconductor layers including an active region;

providing an optical element; and

bonding the semiconductor light emitting device to the optical element effected by a bonding layer disposed between the optical element and the semiconductor light emitting device, wherein the bonding layer comprises a metal oxide.