Vertical LED with current guiding structure

• US 8,148,733 B2
• Filed: 06/15/2011
• Issued: 04/03/2012
• Est. Priority Date: 06/12/2007
• Status: Expired due to Fees

• Current Assignee: Semileds Optoelectronics Company Limited (SemiLEDs Inc)
• Original Assignee: Semileds Optoelectronics Company Limited (SemiLEDs Inc)
• Inventors: Cheng, Hao-Chun, Fan, Feng-Hsu, Chang, Yuan-Hsiao, Liu, Wen-Huang, Chu, Chen-Fu, CHU, JIUNN-YI, Cheng, Chao-Chen
• Primary Examiner(s): Soward, Ida M
• Application Number:
  US13/161,254
• Publication Number:
  US 20110316039A1
• Time in Patent Office: 293 Days
• Field of Search: 257/13, 257/79, 257/94, 257/E33.001, 257/E33.002, 257/E33.012, 257/E33.013, 257/E33.014
• US Class Current: 257/79
• CPC Class Codes: H01L 2224/48091 Arched
• CPC Class Codes: H01L 2224/48465 the other connecting portion not on the bonding area being a wedge bond, i.e. ball-to-wedge, regular stitch
• CPC Class Codes: H01L 2224/4903 Connectors having different sizes, e.g. different diameters
• CPC Class Codes: H01L 27/15 including semiconductor components having potential barriers, specially adapted for light emission
• CPC Class Codes: H01L 2924/00 Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
• CPC Class Codes: H01L 2924/00014 the subject-matter covered by the group, the symbol of which is combined with the symbol of this group, being disclosed without further technical details
• CPC Class Codes: H01L 33/38 with a particular shape
• CPC Class Codes: H01L 33/385 the electrode extending at least partially onto a side surface of the semiconductor body
• CPC Class Codes: H01L 33/40 Materials therefor
• CPC Class Codes: H01L 33/44 characterised by the coatings, e.g. passivation layer or anti-reflective coating

Abstract

Techniques for controlling current flow in semiconductor devices, such as LEDs are provided. For some embodiments, a current guiding structure may be provided including adjacent high and low contact areas. For some embodiments, a second current path (in addition to a current path between an n-contact pad and a metal alloy substrate) may be provided. For some embodiments, both a current guiding structure and second current path may be provided.

Claims

1. A light-emitting diode (LED), comprising:

a metal substrate;

an LED stack for emitting light disposed above the metal substrate, wherein the LED stack comprises;

a p-type semiconductor layer; and

an n-type semiconductor layer disposed above the p-type semiconductor layer, wherein the LED stack provides a first current path for the LED; and

a second current path for the LED different from the first current path.

2. The LED of claim 1, wherein the second current path is coupled between the metal substrate and the n-type semiconductor layer.

3. The LED of claim 2, wherein the second current path forms a non-ohmic contact with the n-type semiconductor layer.

4. The LED of claim 2, wherein the second current path comprises an electrically conductive material.

5. The LED of claim 4, wherein the conductive material comprises multiple metal layers.

6. The LED of claim 4, wherein the conductive material comprises at least one of Ni, Ag, Au, Al, Mo, Pt, W, W—

Si, Ta, Ti, Hf, Ge, Mg, Zn, W/Au, Ta/Au, Pt/Au, Ti/Au, Ti/Al, Ti/Pt/Au, Ti/Ni/Au, Ta/Pt/Au, W—

Si/Au, Cr/Au, Cr/Al, Ni/Au, Ni/Al, Ni/Cu, Cr/Ni/Au, Cr/W/Au, Cr/W—

Si/Au, Cr/Pt/Au, AuGe, AuZn, indium tin oxide (ITO), or indium zinc oxide (IZO).

7. The LED of claim 2, further comprising an electrically insulative material between the second current path and the LED stack.

8. The LED of claim 7, wherein the electrically insulative material comprises a passivation layer adjacent lateral surfaces of the LED stack.

9. The LED of claim 7, wherein the insulative material comprises at least one of SiO₂, Si₃N₄, TiO₂, Al₂O₃, HfO₂, Ta₂O₅, spin-on glass (SOG), MgO, a polymer, polyimide, photoresist, parylene, SU-8, or thermoplastic.

10. The LED of claim 1, wherein the second current path is configured to protect the LED stack from a high-voltage transient.

11. The LED of claim 10, wherein the high-voltage transient comprises an electrostatic discharge (ESD).

12. The LED of claim 2, wherein the second current path comprises a protective device disposed adjacent the n-type semiconductor layer.

13. The LED of claim 12, wherein the protective device comprises at least one of ZnO, ZnS, TiO₂, NiO, SrTiO₃, SiO₂, Cr₂O₃, or polymethyl-methylacrylate (PMMA).

14. The LED of claim 12, wherein the thickness of the protective device is in a range from 1 nm to 10 μ

m.

15. The LED of claim 12, wherein the second current path comprises a bonding layer disposed adjacent the protective device.

16. The LED of claim 15, wherein the second current path comprises a wire coupled between the metal substrate and the bonding layer.

17. The LED of claim 15, wherein the bonding layer comprises multiple metal layers.

18. The LED of claim 15, wherein the bonding layer comprises at least one of Ti/Au, Ti/Al, Ti/Pt/Au, Cr/Au, Cr/Al, Al, Au, Ni/Au, Ni/Al, or Cr/Ni/Au.

19. The LED of claim 15, wherein the thickness of the bonding layer is in a range from 0.5 to 10 μ

m.

20. The LED of claim 1, further comprising a p-electrode interposed between the metal substrate and the LED stack, wherein the p-electrode comprises an electrically conductive structure for guiding current through the LED stack such that the light emitted directly underneath the n-electrode is less than the light emitted from other areas of the LED stack.

21. The LED of claim 20, wherein the current-guiding structure comprises first and second contacts, the first contact having a higher electrical resistance than the second contact.