High efficiency light emitting diodes

• US 5,912,477 A
• Filed: 05/20/1997
• Issued: 06/15/1999
• Est. Priority Date: 10/07/1994
• Status: Expired due to Term

• Current Assignee: CREE Incorporated (Wolfspeed, Inc.)
• Original Assignee: Cree Research, Inc. (Wolfspeed, Inc.)
• Inventors: Negley, Gerald H.
• Primary Examiner(s): GUAY, JOHN FRANCIS
• Application Number:
  US08/859,675
• Time in Patent Office: 756 Days
• Field of Search: 257/76, 257/77, 257/95, 257/94, 257/103, 438/29, 438/33
• US Class Current: 257/95
• CPC Class Codes: B23K 2101/40 Semiconductor devices
• CPC Class Codes: B23K 2103/50 Inorganic material, e.g. metals, not provided for in B23K2103/02 – B23K2103/26
• CPC Class Codes: B23K 2103/52 Ceramics
• CPC Class Codes: B23K 26/16 Removal of by-products, e.g. particles or vapours produced during treatment of a workpiece by a fluid stream B23K26/142
• CPC Class Codes: B23K 26/40 taking account of the properties of the material involved
• CPC Class Codes: H01L 21/0475 Changing the shape of the semiconductor body, e.g. forming recesses, etching of the semiconductor body H01L21/302
• CPC Class Codes: H01L 33/0054 for devices with an active region comprising only group IV elements
• CPC Class Codes: H01L 33/007 comprising nitride compounds
• CPC Class Codes: H01L 33/32 containing nitrogen
• CPC Class Codes: H01L 33/34 containing only elements of Group IV of the Periodic Table
• CPC Class Codes: Y10S 438/94 Laser ablative material removal

Abstract

Light emitting diodes are disclosed which have increased external efficiency and are formed from silicon carbide substrates. Diodes are produced by a method which includes directing a beam of laser light at one surface of a portion of silicon carbide, and which the laser light is sufficient to vaporize the silicon carbide that it strikes to thereby define a cut in the silicon carbide portion; and then dry etching the silicon carbide portion to remove by-products generated when the laser light cuts the silicon carbide portion. The resulting diode structure includes reticulate patterned sidewalls that promote increased light emission efficiency.

Claims

1. A high efficiency light emitting diode comprising:

a silicon carbide substrate that includes reticulate patterned sidewalls;

at least two epitaxial layers on said substrate that form a p-n junction therebetween, said epitaxial layers having reticulate patterned side edges and with the reticulate patterned side edges of said epitaxial layers being coincident with said reticulate patterned sidewalls of said substrate; and

ohmic contacts for applying a potential across said junction;

characterized in that said p-n junction produces an emission in the blue region of the visible spectrum when a potential is applied thereacross.

2. A light emitting diode according to claim 1 characterized in that the junction produces an emission of between about 450 and 490 nanometers (nm).

3. A light emitting diode according to claim 1 wherein said epitaxial layers comprise silicon carbide.

4. A light emitting diode according to claim 1 wherein said epitaxial layers comprise gallium nitride.

5. A high efficiency light emitting diode comprising:

a silicon carbide substrate that includes reticulate patterned sidewalls;

at least two epitaxial layers on said substrate that form a p-n junction therebetween;

said epitaxial layers having reticulate patterned side edges that are coincident with said reticulate patterned sidewalls of said substrate; and

ohmic contacts for applying a potential across said junction.

6. A light emitting diode according to claim 5 wherein said epitaxial layers comprise silicon carbide.

7. A light emitting diode according to claim 5 wherein said epitaxial layers comprise gallium nitride.

8. A light emitting diode according to claim 7 characterized in that the junction produces an emission of between about 350 and 550 nanometers.

9. A light emitting diode according to claim 5 characterized in that said p-n junction produces an emission in the blue region of the visible spectrum when a potential is applied thereacross.

10. A light emitting diode according to claim 9 characterized in that the junction produces an emission of between about 450 and 490 nanometers.

11. A light emitting diode according to claim 5 characterized in that said p-n junction produces an emission in the green region of the visible spectrum when a potential is applied thereacross.

12. A light emitting diode according to claim 11 characterized in that the junction produces an emission of between about 520 and 540 nanometers.

13. A high efficiency light emitting diode comprising:

a silicon carbide substrate that includes reticulate patterned sidewalls;

at least two epitaxial layers on said substrate that form a p-n junction therebetween, said epitaxial layers having reticulate patterned side edges and with the reticulate patterned side edges of said epitaxial layers being coincident with said reticulate patterned sidewalls of said substrate; and

ohmic contacts for applying a potential across said junction;

characterized in that said p-n junction produces an emission in the green region of the visible spectrum when a potential is applied thereacross.

14. A light emitting diode according to claim 13 characterized in that the junction produces an emission of between about 520 and 540 nanometers.

15. A light emitting diode according to claim 13 wherein said epitaxial layers comprise silicon carbide.

16. A light emitting diode according to claim 13 wherein said epitaxial layers comprise gallium nitride.

17. A light emitting diode according to claim 16 characterized in that the junction produces an emission of between about 350 and 550 nanometers.