Three dimensional features on light emitting diodes for improved light extraction

• US 8,263,995 B2
• Filed: 11/02/2010
• Issued: 09/11/2012
• Est. Priority Date: 04/01/2004
• Status: Active Grant

• Current Assignee: CREE Led Incorporated (Smart Global Holdings Incorporated)
• Original Assignee: CREE Incorporated (Wolfspeed, Inc.)
• Inventors: Donofrio, Matthew
• Primary Examiner(s): Chambliss, Alonzo
• Application Number:
  US12/917,960
• Publication Number:
  US 20110068351A1
• Time in Patent Office: 679 Days
• Field of Search: None
• US Class Current: 257/98
• CPC Class Codes: B23K 2101/40 Semiconductor devices
• CPC Class Codes: B23K 2103/50 Inorganic material, e.g. metals, not provided for in B23K2103/02 – B23K2103/26
• CPC Class Codes: B23K 2103/52 Ceramics
• CPC Class Codes: B23K 26/066 by using masks
• CPC Class Codes: B23K 26/40 taking account of the properties of the material involved
• 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 33/32 containing nitrogen
• CPC Class Codes: Y10S 438/94 Laser ablative material removal

Abstract

A method is disclosed for obtaining a high-resolution lenticular pattern on the surface of a light emitting diode. The method comprises imprinting a patterned sacrificial layer of etchable material that is positioned on a semiconductor surface that is in turn adjacent a light emitting active region, and thereafter etching the imprinted sacrificial layer and the underlying semiconductor to transfer an imprinted pattern into the semiconductor layer adjacent the light emitting active region.

Claims

1. A light emitting diode comprising:

at least one light-emitting active layer; and

a patterned semiconductor lenticular surface on the at least one light-emitting active layer, wherein no more than 25 microns of non-lenticular material is provided between the patterned semiconductor lenticular surface and the at least one light-emitting active layer,

wherein the patterned semiconductor lenticular surface on the at least one light-emitting active layer is provided by pressing a flexible embossing stamp into a layer of embossable material to provide a pattern therein and etching the semiconductor lenticular surface according to the pattern to provide the patterned semiconductor lenticular surface.

2. The light emitting diode of claim 1, wherein the patterned semiconductor lenticular surface comprises a plurality of lenticular features that are smaller than 10 microns in their individual footprints.

3. The light emitting diode of claim 1, wherein the patterned semiconductor lenticular surface comprises a plurality of substantially identical lenticular features.

4. The light emitting diode of claim 1, wherein the patterned semiconductor lenticular surface comprises a plurality of lenticular features that are smaller than 6 microns in their individual footprints.

5. The light emitting diode of claim 1, wherein the at least one light-emitting active layer comprises a Group III nitride material.

6. The light emitting diode of claim 5, wherein said patterned semiconductor lenticular surface comprises silicon carbide.

7. A method of providing a patterned semiconductor lenticular surface on a surface of a light emitting diode, the method comprising:

providing a layer of embossable material;

heating the layer of embossable material to a temperature sufficient to soften the layer of embossable material but less than a temperature at which the embossable material will flow;

pressing a flexible embossing stamp including sub-micron patterns into the heated layer of embossable material to provide a high resolution, sub-micron pattern in the layer of embossable material; and

separating the flexible embossing stamp from the layer of embossable material after the layer of embossable material including the high resolution, sub-micron pattern is allowed to cool;

wherein providing a layer of embossable material comprises providing a layer of embossable material on a substrate; and

wherein separating the flexible embossing stamp from the layer of embossable material is followed by etching the substrate according to the high resolution, sub-micron pattern in the layer of embossable material.

8. The method of claim 7, wherein the flexible embossing stamp comprises silicone.

9. A method of providing a patterned semiconductor lenticular surface on a surface of a light emitting diode, the method comprising:

providing a substrate; and

providing a layer of embossable material on the substrate, the layer of embossable material having an index of refraction closely matched to a material of the substrate,

wherein providing the layer of embossable material is followed by;

heating the layer of embossable material to a temperature sufficient to soften the layer of embossable material but less than a temperature at which the embossable material will flow; and

pressing an embossing stamp into the heated layer of embossable material to provide a pattern in the layer of embossable material;

wherein pressing is followed by separating the flexible embossing stamp from the layer of embossable material after the layer of embossable material is allowed to cool; and

wherein separating the flexible embossing stamp from the layer of embossable material is followed by etching the substrate according to the pattern in the layer of embossable material.

10. The method of claim 9, wherein the embossable material comprises a highly transparent, ultraviolet curable material.

11. The method of claim 10, wherein the material of the substrate comprises sapphire and wherein the layer of embossable material has an index of refraction closely matched to sapphire.

12. The method of claim 10, wherein the embossable material comprises a solgel material.

13. The method of claim 12, wherein the material of the substrate comprises sapphire and wherein the solgel material has an index of refraction closely matched to sapphire.