GaN LEDs with improved area and method for making the same

• US 9,018,643 B2
• Filed: 09/13/2013
• Issued: 04/28/2015
• Est. Priority Date: 09/06/2011
• Status: Active Grant

• Current Assignee: Alpad Corporation
• Original Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Inventors: Yang, Long
• Primary Examiner(s): McCall Shepard, Sonya D
• Application Number:
  US14/026,556
• Publication Number:
  US 20140167082A1
• Time in Patent Office: 592 Days
• Field of Search: None
• US Class Current: 257/81
• CPC Class Codes: H01L 33/0093 Wafer bonding; Removal of the growth substrate
• CPC Class Codes: H01L 33/0095 Post-treatment of devices, e.g. annealing, recrystallisation or short-circuit elimination
• CPC Class Codes: H01L 33/24 of the light emitting region, e.g. non-planar junction
• CPC Class Codes: H01L 33/405 Reflective materials

Abstract

Enlightening device and method for making the same are disclosed. Individual light emitting devices such as LEDs are separated to form individual dies by process in which a first narrow trench cuts the light emitting portion of the device and a second trench cuts the substrate to which the light emitting portion is attached. The first trench can be less than 10 μm. Hence, a semiconductor area that would normally be devoted to dicing streets on the wafer is substantially reduced thereby increasing the yield of devices. The devices generated by this method can also include base members that are electrically conducting as well as heat conducting in which the base member is directly bonded to the light emitting layers thereby providing improved heat conduction.

Claims

1. A device comprising:

a structure including a first semiconductor layer, a second semiconductor layer, a light emitting layer formed between said first semiconductor layer and said second semiconductor layer, and a reflective layer formed on a first surface of said second semiconductor layer that is opposite to a second surface in contact with said active layer, a first edge defining a lateral size of said structure; and

a base member including a substrate and a bonding layer formed on said substrate, said structure formed in contact with said bonding layer, a second edge defining a lateral size of said base member,

wherein a lateral size of said reflective layer is substantially equal to a lateral size of said active layer, and

said first edge at said reflective layer and said second edge at said bonding layer are formed having a difference in level so that a lateral size of said bonding layer is smaller than said lateral size of said reflective layer by at least said difference in level between said first edge at said reflective layer and said second edge at said bonding layer.

2. The device of claim 1, wherein said base member has a first surface in contact with said reflective layer, a lateral size of said first surface of said base member being substantially equal to said lateral size of said reflective layer.

3. The device of claim 2, wherein said base member has a lateral size at a location distal from said first surface of said base member smaller than said lateral size of said first surface of said base member.

4. The device of claim 1, wherein said light emitting layer emits light of a predetermined wavelength, and said first layer comprises an n-GaN layer with a surface that includes scattering features having a dimension greater than said predetermined wavelength.

5. The device of claim 1, wherein said base member has a thickness greater than 100 μ

m.

6. The device of claim 1, wherein said base member comprises an electrical conductor.

7. The device of claim 1, wherein said substrate comprises crystalline silicon.

8. The device of claim 1, wherein said base member comprises a metal.

9. The device of claim 8, wherein said metal is copper or nickel.

10. The device of claim 1, further comprising a dielectric layer formed between said second semiconductor layer and said reflective layer, said dielectric layer having vias.

11. The device of claim 1, wherein said base member includes an insulating pad, and said base member has a first surface in contact with said reflective layer, said first surface of said base member including a surface of said insulating pad and a surface of said bonding layer.

12. The device of claim 1, wherein said substrate has a first surface upon which said bonding layer is formed, said first surface of said substrate is smaller than said lateral size of said reflective layer, said substrate having a lateral size at a location distal from said first surface of said substrate smaller than said lateral size of said first surface of said substrate.

13. The device of claim 1, wherein said bonding layer is a eutectic metal layer.

14. The device of claim 13, wherein said base member includes an insulating layer between said eutectic metal layer and the substrate.

15. The device of claim 1, further comprising a transparent conductive layer formed between said second semiconductor layer and said reflective layer.

16. The device of claim 10, further comprising a transparent conductive layer formed between said second semiconductor layer and said reflective layer, wherein said reflective layer is in electrical contact with said transparent conductive layer through said vias.

17. The device of claim 15, wherein said transparent conductive layer is an ITO layer.

18. The device of claim 16, wherein said transparent conductive layer is an ITO layer.

19. The device of claim 1, said difference in level is formed in a step form.