Distributed current blocking structures for light emitting diodes

• US 8,564,010 B2
• Filed: 08/04/2011
• Issued: 10/22/2013
• Est. Priority Date: 08/04/2011
• Status: Active Grant

• Current Assignee: Alpad Corporation
• Original Assignee: Toshiba Techno Center Inc. (Toshiba Corporation)
• Inventors: Chuang, Chih-Wei, Lin, Chao-Kun
• Primary Examiner(s): Fulk, Steven J
• Assistant Examiner(s): WARD, ERIC A
• Application Number:
  US13/198,664
• Publication Number:
  US 20130032847A1
• Time in Patent Office: 810 Days
• Field of Search: 257 79-103, 257E33001-E33077, 438 22- 47
• US Class Current: 257/99
• CPC Class Codes: H01L 2933/0016 relating to electrodes
• CPC Class Codes: H01L 33/14 with a carrier transport control structure, e.g. highly-doped semiconductor layer or current-blocking structure
• CPC Class Codes: H01L 33/145 with a current-blocking structure
• CPC Class Codes: H01L 33/22 Roughened surfaces, e.g. at the interface between epitaxial layers
• CPC Class Codes: H01L 33/38 with a particular shape
• CPC Class Codes: H01L 33/387 with a plurality of electrode regions in direct contact with the semiconductor body and being electrically interconnected by another electrode layer
• CPC Class Codes: H01L 33/405 Reflective materials
• CPC Class Codes: H01L 33/42 Transparent materials

Abstract

An LED device includes a strip-shaped electrode, a strip-shaped current blocking structure and a plurality of distributed current blocking structures. The current blocking structures are formed of an insulating material such as silicon dioxide. The strip-shaped current blocking structure is located directly underneath the strip-shaped electrode. The plurality of current blocking structures may be disc shaped portions disposed in rows adjacent the strip-shaped current blocking structure. Distribution of the current blocking structures is such that current is prevented from concentrating in regions immediately adjacent the electrode, thereby facilitating uniform current flow into the active layer and facilitating uniform light generation in areas not underneath the electrode. In another aspect, current blocking structures are created by damaging regions of a p-GaN layer to form resistive regions. In yet another aspect, current blocking structures are created by etching away highly doped contact regions to form regions of resistive contact between conductive layers.

Claims

1. A Light Emitting Diode (LED) comprising:

a strip-shaped electrode, wherein current flow through the strip-shaped electrode causes light to be emitted from the LED;

a strip-shaped current blocking structure disposed directly underneath the strip-shaped electrode, wherein the strip-shaped current blocking structure extends in a first direction, wherein a first square area A, a second square area B, and a third square area C abut one another and extend in the order A, B, C in a row in a second direction perpendicular to the first direction and away from the strip-shaped current blocking structure, wherein each of A, B and C is a square area of 400 square microns; and

a plurality of current blocking structures, wherein at least a first one of the plurality of current blocking structures covers at least part of A, wherein at least a second one of the plurality of current blocking structures covers at least part of B, wherein at least a third one of the plurality of current blocking structures covers at least part of C, wherein the plurality of current blocking structures covers X percent of A, covers Y percent of B, and covers Z percent of C, and wherein X>

Z.

2. The LED of claim 1, wherein X>

Y and Y>

Z.

3. The LED of claim 1, wherein each of the plurality of current blocking structures is a disc of a substantially identical circular area.

4. The LED of claim 3, wherein each of the discs has a diameter less than five microns.

5. The LED of claim 1, wherein each of the plurality of current blocking structures covers an area of less than approximately twenty square microns.

6. The LED of claim 3, wherein the plurality of current blocking structures are disposed in rows, and wherein each of the rows extends in a direction parallel to the first direction.

7. The LED of claim 6, wherein adjacent ones of the current blocking structures of a first of the rows are separated by a first distance, and wherein adjacent ones of the current blocking structures of a second of the rows are separated by a second distance, and wherein the first distance is smaller than the second distance.

8. The LED of claim 1, wherein a layer of a transparent conductor is conformal with the strip-shaped current blocking structure and with the plurality of current blocking structures.

9. The LED of claim 1, wherein a layer of silver is conformal with the strip-shaped current blocking structure and with the plurality of current blocking structures.

10. The LED of claim 1, wherein the strip-shaped current blocking structure and the plurality of current blocking structures are structures of a material taken from the group consisting of:

silicon dioxide and silicon nitride.

11. The LED of claim 1, wherein the LED comprises a layer of semiconductor material having relatively more conductive portions and having relatively less conductive portions, and wherein the strip-shaped current blocking structure and the plurality of current blocking structures together comprise the relatively less conductive portions.

12. The LED of claim 1, wherein none of the plurality of current blocking structures is contacting the strip-shaped current blocking structure.

13. The LED of claim 1, wherein the strip-shaped current blocking structure and the plurality of current blocking structures are disposed on a planar surface.

14. The LED of claim 1, wherein the strip-shaped electrode and the strip-shaped current blocking structure are of approximately the same width and extend parallel to one another.

15. A method of manufacturing a Light Emitting Diode (LED) comprising:

forming a strip-shaped current blocking structure, wherein the strip-shaped current blocking structure extends in a first direction, wherein a first square area A, a second square area B, and a third square area C abut one another and extend in the order A, B, C in a row in a second direction perpendicular to the first direction and away from the strip-shaped current blocking structure, wherein each of A, B and C is a square area of 400 square microns; and

forming a plurality of current blocking structures, wherein at least a first one of the plurality of current blocking structures covers at least part of A, wherein at least a second one of the plurality of current blocking structures covers at least part of B, wherein at least a third one of the plurality of current blocking structures covers at least part of C, wherein the plurality of current blocking structure covers X percent of A, covers Y percent of B, and covers Z percent of C, and wherein X>

Z; and

forming a strip-shaped electrode so that the strip-shaped electrode is disposed directly above the strip-shaped current blocking structure, wherein current flow through the strip-shaped electrode causes light to be emitted from the LED.

16. A Light Emitting Diode (LED) comprising:

a strip-shaped electrode, wherein current flow through the strip-shaped electrode causes light to be emitted from the LED;

a strip-shaped current blocking structure disposed directly underneath the strip-shaped electrode, wherein the strip-shaped current blocking structure extends in a first direction, wherein a first square area A, a second square area B, and a third square area C abut one another and extend in the order A, B, C in a row in a second direction perpendicular to the first direction and away from the strip-shaped current blocking structure, wherein each of A, B and C is a square area of 400 square microns; and

means for blocking current flow in selected areas of A, B and C such that a first current flow through A is substantially equal to a second current flow through B and such that the second current flow through B is substantially equal to a third current flow through C.

17. The LED of claim 16, wherein the means is a plurality of separate features, and wherein none of the separate features is contacting the strip-shaped current blocking structure.

18. The LED of claim 16, wherein the means is a two-dimensional array of disc shaped features of an insulating material.

19. Light Emitting Diode (LED) comprising:

a strip-shaped electrode, wherein a current flow through the strip-shaped electrode causes light to be emitted from the LED;

an active layer, wherein a portion of the active layer is disposed under the strip-shaped electrode; and

a current blocking layer comprising a plurality of portions, wherein each portion of the current blocking layer has a porosity and partially covers a corresponding portion of a surface, wherein the porosity of a portion of the current blocking layer is a percentage of the corresponding portion of the surface that is not covered by the current blocking layer, wherein the porosity varies across the current blocking layer from portion to portion such that the current flow flows through the current blocking layer and to the active layer and such that current flow through the active layer is substantially uniform in all portions of the active layer except for portions of the active layer disposed underneath the strip-shaped electrode where there is substantially no current flow.