Method and structure for improved LED light output

• US 7,095,052 B2
• Filed: 10/22/2004
• Issued: 08/22/2006
• Est. Priority Date: 10/22/2004
• Status: Active Grant

• Current Assignee: Avago Technologies International Sales Pte Limited (Broadcom, Inc.)
• Original Assignee: Avago Technologies ECBU IP Singapore Pte Limited (Broadcom, Inc.)
• Inventors: Lester, Steven D.
• Primary Examiner(s): Nelms, David
• Assistant Examiner(s): HO, HOANG QUAN TRAN
• Application Number:
  US10/971,380
• Publication Number:
  US 20060097269A1
• Time in Patent Office: 669 Days
• Field of Search: None
• US Class Current: 257/79
• CPC Class Codes: H01L 33/08 with a plurality of light emitting regions, e.g. laterally discontinuous light emitting layer or photoluminescent region integrated within the semiconductor body H01L27/15 takes precedence

Abstract

The efficiency of LEDs is increased by incorporating multiple active in series separated by tunnel junction diodes. This also allows the LEDs to operate at longer wavelengths.

Claims

1. A light emitting diode structure comprising:

a substrate; and

a plurality of layer structures formed on said substrate, each one of said plurality of layer structures comprising a tunnel junction and a quantum well active region surrounded by a pair of cladding layers, said plurality of layer structures arranged in a vertical stack with respect to said substrate such that a first one of said plurality of layer structures is closest to said substrate and a second one of said plurality of layer structures is furthest from said substrate.

2. The structure of claim 1 wherein said cladding layer is comprised of AlGaInN.

3. The structure of claim 1 wherein said substrate is comprised of a material selected from the group containing Al₂O₃, SiC, AlN, and GaN.

4. The structure of claim 1 wherein said tunnel junction is comprised of an n doped AlGaInN layer.

5. The structure of claim 4 wherein said n doped AlGaInN layer is doped to a concentration in the range from about 2·

10²⁰/cm³ to about 3·

10²⁰/cm³ with an n dopant.

6. The structure of claim 5 wherein said n dopant is silicon.

7. The structure of claim 4 wherein said n doped AlGInN layer has a thickness in the range from about 100 to about 500 angstroms.

8. The structure of claim 1 wherein said tunnel junction is comprised of a p doped AlGaInN layer.

9. The structure of claim 1 wherein said quantum well active region is comprised of a plurality of InGaN quantum wells separated from each other by GaN barrier layers.

10. The structure of claim 1 wherein said tunnel junction is operable to be reverse biased.

11. A method for forming a light emitting diode structure comprising:

a substrate; and

forming a plurality of layer structures on said substrate, each one of said plurality of layer structures comprising a tunnel junction and a quantum well active region surrounded by a pair of cladding layers, said plurality of layer structures arranged in a vertical stack with respect to said substrate such that a first one of said plurality of layer structures is closest to said substrate and a second one of said plurality of layer structures is furthest from said substrate.

12. The method of claim 11 wherein said cladding layer is comprised of AlGaInN.

13. The method of claim 11 wherein said substrate is comprised of a material selected from the group containing Al₂O₃, SiC and GaN.

14. The method of claim 11 wherein said tunnel junction is comprised of an n doped AlGaInN layer.

15. The method of claim 14 wherein said n doped AlGaInN layer is doped to a concentration in the range from about 2·

10²⁰/cm³ to about 3·

10²⁰/cm³ with an n dopant.

16. The method of claim 15 wherein said n dopant is silicon.

17. The method of claim 14 wherein said n doped AlGaInN layer has a thickness in the range from about 100 to about 500 angstroms.

18. The method of claim 11 wherein said tunnel junction is comprised of a p doped AlGaInN layer.

19. The method of claim 11 wherein said quantum well active region is comprised of a plurality of InGaN quantum wells separated from each other by GaN barrier layers.

20. The method of claim 11 wherein said tunnel junction is operable to be reverse biased.