Ultraviolet light emitting device having current blocking layer

• US 10,340,418 B2
• Filed: 01/08/2018
• Issued: 07/02/2019
• Est. Priority Date: 01/06/2017
• Status: Active Grant

• Current Assignee: Seoul Viosys Co., Ltd. (Seoul Semiconductor Co., Ltd.)
• Original Assignee: Seoul Viosys Co., Ltd. (Seoul Semiconductor Co., Ltd.)
• Inventors: Kim, Ye Seul, Kim, Kyoung Wan, Kim, Ji Hye, Woo, Sang Won
• Primary Examiner(s): Nguyen, Khiem D
• Application Number:
  US15/865,051
• Publication Number:
  US 20180198023A1
• Time in Patent Office: 540 Days
• 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 33/20 with a particular shape, e.g. curved or truncated substrate
• CPC Class Codes: H01L 33/38 with a particular shape
• CPC Class Codes: H01L 33/405 Reflective materials
• CPC Class Codes: H01L 33/46 Reflective coating, e.g. dielectric Bragg reflector

Abstract

Described herein is a highly efficient light emitting device. The light emitting device includes: a first conductivity-type semiconductor layer; a second conductivity-type semiconductor layer; an active layer interposed between the first conductivity-type semiconductor layer and the second conductivity-type semiconductor layer; a current blocking layer disposed on the second conductivity-type semiconductor layer; a transparent electrode layer covering the current blocking layer; a first electrode electrically connected to the first conductivity-type semiconductor layer; a second electrode disposed on the transparent electrode layer and electrically connected to the transparent electrode layer, the second electrode including a second electrode pad and a second electrode extension extending from the second electrode pad; and a second reflective layer interposed between the second electrode and the transparent electrode layer, wherein each of the second electrode pad and the second electrode extension covers at least part of the current blocking layer.

Claims

1. A light emitting device comprising:

a first conductivity-type semiconductor layer;

a second conductivity-type semiconductor layer;

an active layer interposed between the first conductivity-type semiconductor layer and the second conductivity-type semiconductor layer;

a current blocking layer disposed on the second conductivity-type semiconductor layer;

a transparent electrode layer covering the current blocking layer;

a first electrode electrically connected to the first conductivity-type semiconductor layer;

a second electrode disposed on the transparent electrode layer and electrically connected to the transparent electrode layer, the second electrode comprising a second electrode pad and a second electrode extension extending from the second electrode pad; and

an insulating layer disposed under the first electrode; and

a first reflective layer interposed between the first electrode and the insulting layer;

a second reflective layer interposed between the second electrode and the transparent electrode layer and having a curved shape,

wherein each of the second electrode pad and the second electrode extension covers at least part of the current blocking layer; and

wherein the second reflective layer includes at least one recess indented into the curved shape.

2. The light emitting device according to claim 1, wherein the second reflective layer comprises dielectric layers having different indices of refraction.

3. The light emitting device according to claim 1, wherein the second electrode is confined within an upper region of the current blocking layer.

4. The light emitting device according to claim 1, wherein the current blocking layer comprises a first current blocking layer corresponding to the second electrode pad and a second current blocking layer corresponding to the second electrode extension.

5. The light emitting device according to claim 4, wherein the second reflective layer comprises a reflective layer interposed between the second electrode pad and the first current blocking layer.

6. The light emitting device according to claim 1, wherein the recess is placed in an upper region of the current blocking layer and at least part of a lower surface of the second electrode pad is connected to the transparent electrode layer through the recess of the second reflective layer.

7. The light emitting device according to claim 4, wherein the second reflective layer comprises a reflective layer disposed in the form of dots between the second electrode extension and the transparent electrode layer, the reflective layer having a greater width than the second electrode extension.

8. The light emitting device according to claim 7, wherein the reflective layer is confined within an upper region of the current blocking layer.

9. The light emitting device according to claim 1, wherein the first electrode comprises a first electrode pad and a first electrode extension extending from the first electrode pad,

the first electrode pad being disposed above the second conductivity-type semiconductor layer, and

the insulating layer insulates the first electrode pad from the second conductivity-type semiconductor layer.

10. The light emitting device according to claim 9, wherein the first reflective layer comprises a reflective layer disposed between the first electrode pad and the second conductivity-type semiconductor layer, the reflective layer having an area smaller than the insulating layer and larger than the first electrode pad.

11. The light emitting device according to claim 10, wherein the first reflective layer comprises a reflective layer disposed in the form of dots under the first electrode extension, the reflective layer having a greater width than the first electrode extension.

12. The light emitting device according to claim 11, wherein the second reflective layer comprises a reflective layer disposed in the form of dots between the second electrode extension and the transparent electrode layer, the reflective layer having a greater width than the second electrode extension, and the dots of the second reflective layer and the dots of the first reflective layer are alternately arranged.

13. The light emitting device according to claim 1, wherein the first electrode comprises a first electrode pad and a first electrode extension extending from the first electrode pad,

the first electrode pad being disposed above the first conductivity-type semiconductor layer, and

the insulating layer has a smaller area than the first electrode pad and is disposed in some region between the first electrode pad and the first conductivity-type semiconductor layer.

14. The light emitting device according to claim 13, wherein an area of the insulating layer interposed between the first electrode pad and the first conductivity-type semiconductor layer is less than 90% of an area of the first electrode pad.

15. The light emitting device according to claim 1, wherein the active layer and the second conductivity-type semiconductor layer are structured to provide a mesa,

wherein the mesa comprises at least one groove formed on a side surface thereof such that the first conductivity-type semiconductor layer is partially exposed through the groove, the insulating layer comprises an opening at least partially exposing the exposed first conductivity-type semiconductor layer, and the first electrode extension is connected to the first conductivity-type semiconductor layer through the opening.

16. The light emitting device according to claim 15, wherein the second reflective layer comprises a reflective layer disposed in the form of dots between the second electrode extension and the transparent electrode layer, the reflective layer having a greater width than the second electrode extension, and

the dots of the second reflective layer and the at least one groove of the mesa are alternately arranged.

17. The light emitting device according to claim 1, wherein the current blocking layer includes a single layer and the second reflective layer comprises a plurality of layers having different indices of refraction.

18. The light emitting device according to claim 17, wherein the second reflective layer comprises a first region and a second region,

the first region formed with a single layer placed at a lowermost side of the second reflective layer,

the second region comprising a plurality of layers placed on the first region.

19. The light emitting device according to claim 18, wherein the first region has a thickness of 7/(4*n1)*λ

and each of the layers in the second region has a thickness of 1/(4*n2)*λ

(λ

is the wavelength of light generated from the active layer, n1 is the index of refraction of the first region, and n2 is the index of refraction of each of the layers in the second region).