LIGHT-EMITTING ELEMENT COMPRISING A REFLECTIVE STRUCTURE WITH HIGH EFFICIENCY

• US 20140209949A1
• Filed: 01/23/2014
• Published: 07/31/2014
• Est. Priority Date: 01/25/2013
• Status: Active Grant

• Current Assignee: Epistar Corporation (Ennostar, Inc.)
• Original Assignee: Epistar Corporation (Ennostar, Inc.)
• Inventors: CHUANG, Keng-Lin, TSENG, Chun-Lung, SU, Chih-Tsung, SHEN, Ching-Hsing, LIU, Chih-Hui Alston, KUN, Yu-Ming
• Granted Patent: US 9,240,519 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 33/46 Reflective coating, e.g. dielectric Bragg reflector

Abstract

A light-emitting element, comprises: a substrate; a light-emitting semiconductor stack over the substrate and comprising an active layer; and a Distributed Bragg reflective unit under the substrate comprising a first Distributed Bragg reflective structure under the substrate and comprising a first number of pairs of alternately stacked first sub-layers and second sub-layers, and a second Distributed Bragg reflective structure under the first Distributed Bragg reflective structure and comprising a second number of pairs of alternately stacked third sub-layers and fourth sub-layers, wherein the first number is different from the second number.

Claims

1. A light-emitting element, comprising:

a substrate;

a light-emitting semiconductor stack over the substrate and comprising an active layer; and

a Distributed Bragg reflective unit under the substrate comprising a first Distributed Bragg reflective structure under the substrate and comprising a first number of pairs of alternately stacked first sub-layers and second sub-layers, and a second Distributed Bragg reflective structure under the first Distributed Bragg reflective structure and comprising a second number of pairs of alternately stacked third sub-layers and fourth sub-layers, wherein the first number is different from the second number.

2. The light-emitting element according to claim 1, comprising a metal reflective layer under the second Distributed Bragg reflective structure.

3. The light-emitting element according to claim 1, wherein the light-emitting semiconductor stack comprises III-nitride material, III-phosphide material, or III-arsenide material.

4. The light-emitting element according to claim 1, wherein a total thickness of the first Distributed Bragg reflective structure is larger than a total thickness of the second Distributed Bragg reflective structure.

5. The light-emitting element according to claim 1, wherein each first sub-layer is closer to the substrate than the second sub-layer in a same pair of the first Distributed Bragg reflective structure, wherein a thickness of the first sub-layer is smaller than a thickness of the second sub-layer.

6. The light-emitting element according to claim 5, wherein a refractive index of the first sub-layer is larger than that of the second sub-layer.

7. The light-emitting element according to claim 1, wherein each third sub-layer of is closer to the substrate than the fourth sub-layer in a same pair of the second Distributed Bragg reflective structure, wherein a thickness of the third sub-layer is smaller than a thickness of the fourth sub-layer.

8. The light-emitting element according to claim 7, wherein a refractive index of the third sub-layer is larger than that of the fourth sub-layer.

9. The light-emitting element according to claim 1, wherein each first sub-layer of is closer to the substrate than the second sub-layer in a same pair of the first Distributed Bragg reflective structure, and each third sub-layer of the pairs is closer to the substrate than the fourth sub-layer in a same pair of the second Distributed Bragg reflective structure, wherein a thickness of the first sub-layer is larger than a thickness of the third sub-layer, and a thickness of the second sub-layer is larger than a thickness of the fourth sub-layer.

10. The light-emitting element according to claim 9, wherein a refractive index of the first sub-layer or a refractive index of the third sub-layer is larger than 2.

11. The light-emitting element according to claim 9, wherein a material of the first sub-layer or a material of the third sub-layer comprises TiO₂, HfO₂, ZnO, Ta₂O₅, Nb₂O₅, or the combinations thereof.

12. The light-emitting element according to claim 9, wherein a material of the second sub-layer or a material of the fourth sub-layer comprises SiO₂, LaF₃, MgF₂, NaF, Na₃AlF₆, CaF₂, or the combinations thereof.

13. The light-emitting element according to claim 1, comprising a window layer between the substrate and the first Distributed Bragg reflective structure.

14. The light-emitting element according to claim 1, wherein the substrate comprises a first portion and a second portion surrounding the first portion, wherein the second portion has a thickness smaller than a thickness of the first portion.

15. The light-emitting element according to claim 14, wherein the second portion comprises a minimum thickness not more than 80% of a thickness of the first portion.

16. The light-emitting element according to claim 1, wherein the substrate has a textured surface directly above the Distributed Bragg reflective unit.

17. The light-emitting element according to claim 16, wherein the Distributed Bragg reflective unit is conformably formed on the textured surface.

18. The light-emitting element according to claim 17, further comprising a metal reflective layer under the second Distributed Bragg reflective structure.

19. The light-emitting element according to claim 18, wherein the metal reflective layer covers the second portion of the substrate.

20. A light-emitting element, comprising:

a substrate comprising a first portion and a second portion surrounding the first portion, wherein the second portion has a thickness smaller than a thickness of the first portion;

a light-emitting semiconductor stack over the substrate and comprising an active layer; and

a first electrode and a second electrode comprising an electrical polarity different from that of the first electrode;

wherein the first electrode and the second electrode are over a same side of the substrate.