Light emitting devices with low packaging factor

• US 8,957,440 B2
• Filed: 10/04/2011
• Issued: 02/17/2015
• Est. Priority Date: 10/04/2011
• Status: Active Grant

• Current Assignee: CREE Led Incorporated (Smart Global Holdings Incorporated)
• Original Assignee: CREE Incorporated (Wolfspeed, Inc.)
• Inventors: Ibbetson, James, Emerson, David Todd
• Primary Examiner(s): Warren, Matthew E
• Application Number:
  US13/252,448
• Publication Number:
  US 20130082291A1
• Time in Patent Office: 1,232 Days
• Field of Search: 257 98-100, 257/E33.067
• US Class Current: 257/98
• CPC Class Codes: H01L 2224/48091 Arched
• 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 33/22 Roughened surfaces, e.g. at the interface between epitaxial layers
• CPC Class Codes: H01L 33/405 Reflective materials
• CPC Class Codes: H01L 33/46 Reflective coating, e.g. dielectric Bragg reflector
• CPC Class Codes: H01L 33/54 having a particular shape

Abstract

A light emitting diode die that when encapsulated within an overmolded hemispherical lens has a packaging factor less than 1.2. The light emitting diode die may include a stacked structure including a metal overlay, a composite high reflectivity mirror on the metal overlay, a transparent conductive oxide layer on the composite high reflectivity mirror, and a diode structure on the transparent conductive oxide layer. The diode structure may include a roughened surface opposite the transparent conductive oxide layer, a submount connected to the composite high reflectivity mirror and a bond metal between the submount and the metal overlay. A conductive via may extend through the composite high reflectivity mirror and electrically connect the transparent conductive oxide and the bond metal.

Claims

1. A light emitting diode die comprising:

a metal overlay;

a composite high reflectivity mirror comprising a plurality of alternating stacked layers of SiO2 and at least one of TiO2 and Ta2O5 on the metal overlay;

a submount connected to the metal overlay by a bond metal;

a transparent conductive oxide layer on the composite high reflectivity mirror;

a diode structure on the transparent conductive oxide layer; and

an overmolded hemispherical lens,

wherein the metal overlay, the composite high reflectivity mirror, the transparent conductive oxide layer are arranged such that the light emitting diode die is configured to exhibit a total power of light output divided by total power extracted from the light emitting diode die without the overmolded hemispherical lens that is less than 1.2.

2. The light emitting diode die of claim 1 exhibiting a total power of light output divided by total power extracted from the light emitting diode die without the overmolded hemispherical lens that is less than 1.18.

3. The light emitting diode die of claim 1 characterized by exhibiting a total power of light output die divided by total power extracted from the light emitting diode die without the overmolded hemispherical lens that is less than 1.16.

4. The light emitting diode die of claim 1 characterized by exhibiting a total power of light output divided by total power extracted from the light emitting diode die without the overmolded hemispherical lens that is greater than 1 and less than 1.14.

5. The light emitting diode die of claim 1, wherein the diode structure comprises a roughened surface opposite the transparent conductive oxide layer comprising at least one of ZnO, ZnS, MgO, In2O3, CdS, TiO2, PbO, ZnSnO and indium tin oxide (ITO) such that when the light emitting diode die is encapsulated within the overmolded hemispherical lens, the light emitting diode die is characterized by exhibiting a total power of light output divided by total power extracted from the light emitting diode die without encapsulation that is less than 1.2.

6. The light emitting diode of claim 1, further comprising a conductive via extending through the composite high reflectivity mirror and electrically connecting the transparent conductive oxide and the bond metal.

7. The light emitting diode of claim 1, wherein the composite high reflectivity mirror comprises a plurality of alternating stacked layers of SiO2 and Ta2O5 with respective thicknesses of the alternating stacked layers selected such that the light emitting diode die is characterized by exhibiting a total power of light output divided by total power extracted from the light emitting diode die without the overmolded hemispherical lens that is less than 1.2.

8. The light emitting diode of claim 7, wherein the composite high reflectivity mirror further comprising a layer of Al2O3 on an outermost layer of SiO2 opposite the diode structure configured with a thickness such that the light emitting diode die is characterized by exhibiting a total power of light output divided by total power extracted from the light emitting diode die without the overmolded hemispherical lens that is less than 1.2.

9. The light emitting diode of claim 1, wherein the transparent conductive oxide comprises indium tin oxide with a thickness of about 50 nm.

10. The light emitting diode of claim 9, wherein a total thickness of the transparent conductive oxide, the composite high reflectivity mirror and the metal overlay is about 0.75 microns.

11. The light emitting diode of claim 1, wherein the light emitting diode comprises a surface emitting light emitting diode having a lambertian emission pattern.

12. The light emitting diode of claim 1, wherein the metal overlay comprises about a 200 nm layer of Ag and about a 100 nm layer of TiW.

13. The light emitting diode of claim 1, wherein the reflectance of the composite high reflectivity mirror is configured such that the light emitting diode die is characterized by exhibiting a total power of light output divided by total power extracted from the light emitting diode die without the encapsulant dome that is less than 1.2.

14. The light emitting diode of claim 1, wherein the overmolded hemispherical lens is a silicone lens having an index of refraction of 1.5 and forms a dome over the light emitting diode die, wherein the dome has a width at least three times a width of the light emitting diode die.

15. The light emitting diode of claim 1, wherein the diode structure comprises a GaN-based quantum well active region between a p-type AlInGaN region and an n-type AlInGaN region.

16. A light emitting diode package comprising:

a submount;

a light emitting diode on the submount; and

an encapsulant dome on the light emitting diode;

wherein the light emitting diode package comprises a metal overlay, a composite high reflectivity mirror comprising a layer of Al2O3 on an outermost layer of SiO2 opposite the light emitting diode and a transparent conductive oxide layer with respective thicknesses selected such that the light emitting diode die is configured to exhibit a total power of light output divided by total power extracted from the light emitting diode without the encapsulant dome that is less than 1.2.

17. A light emitting diode die comprising:

a submount;

a metal overlay connected to the submount comprising at least one of a layer of silver and a layer of tin, wherein the metal overlay is attached to the submount by a bond metal of at least one of gold and tin;

a composite high reflectivity mirror on the metal overlay comprising;

a plurality of alternating stacked layers of SiO2 and at least one of TiO2 and Ta2O5, wherein the plurality of alternating stacked layers have different thicknesses; and

a layer of Al2O3 on an outermost layer of SiO2 opposite the diode structure;

a transparent conductive oxide layer on the composite high reflectivity mirror;

a diode structure comprising a GaN-based quantum well active region between a p-type AlInGaN region and an n-type AlInGaN region on the transparent conductive oxide layer; and

an overmolded hemispherical lens over at least the composite high reflectivity mirror and the diode structure, wherein the Al2O3 layer, the layers of SiO2 and the layers of the at least one of Ta2O5 and TiO2 are configured with respective thicknesses to reflect light from the diode structure having a wavelength between 460 nm and 600 nm in an amount and pattern such that the overmolded hemispherical lens increases a total power of light output from the light emitting diode die by less than 20%.

18. The light emitting diode die of claim 17, wherein the outermost layer of SiO2 is a first SiO2 layer, and wherein the composite high reflectivity mirror further comprises:

a first at least one of Ta2O5 and TiO2 layer on the first SiO2 layer and having a thickness less than the first SiO2 layer;

a second SiO2 layer having a thickness greater than the first at east one of Ta2O5 and TiO2 layer;

a second at least one of Ta2O5 and TiO2 layer having a thickness less than the first at least one of Ta2O5 and TiO2 layer; and

a third SiO2 layer having a thickness less than the second at least one of Ta2O5 and TiO2 layer, wherein the Al2O3 layer has a thickness less than the third SiO2 layer.

19. The light emitting diode die of claim 18, wherein a total thickness of the transparent conductive oxide, the composite high reflectivity mirror and the metal overlay is about 0.75 microns.

20. The light emitting diode die of claim 19, wherein the first SiO2 layer has a total thickness of about 4500 Angstroms.