Light-emitting diode with a structured surface

• US 6,649,939 B1
• Filed: 06/25/2002
• Issued: 11/18/2003
• Est. Priority Date: 09/10/1999
• Status: Expired due to Term

• Current Assignee: OSRAM OLED GMBH (Ams-Osram AG)
• Original Assignee: Osram Opto Semiconductors GmbH (Ams-Osram AG)
• Inventors: Wirth, Ralph
• Primary Examiner(s): Tran, Minh Loan
• Assistant Examiner(s): TRAN, TAN N
• Application Number:
  US10/070,584
• Time in Patent Office: 511 Days
• Field of Search: 257/95, 257/98, 257/91, 257/99, 257/744, 257/745, 362/296, 362/341, 362/327, 362/346, 362/347, 362/348, 362/349, 362/350, 362/800
• US Class Current: 257/95
• CPC Class Codes: H01L 33/025 Physical imperfections, e.g. particular concentration or distribution of impurities
• CPC Class Codes: H01L 33/20 with a particular shape, e.g. curved or truncated substrate

Abstract

For improving the light output, a light-emitting diode has at least one section of a light exit-side surface covered with a plurality of truncated pyramids. Light radiations, which are emitted by a light-generating layer, enter into the truncated pyramids through a base area and are efficiently coupled out of the sidewalls of the pyramids.

Claims

1. A light-emitting diode comprising:

a semiconductor layer structure containing a substrate and at least one light-generating layer formed on the substrate,

a first electrical contact layer on the substrate and

a second electrical contact layer on at least one section of a surface of the semiconductor structure lying opposite the substrate,

the surface of the semiconductor structure lying opposite the substrate being structured over at least one section to have a plurality of truncated elements selected from truncated pyramids and truncated cones outside a region of the second electrical contact layer.

2. The light-emitting diode according to claim 1, wherein the truncated elements are three-sided truncated pyramids.

3. The light-emitting diode according to claim 1, wherein the truncated elements are truncated pyramids having at least four sides.

4. The light-emitting diode according to claim 1, wherein the section of the surface lying opposite the substrate that is covered with the second electrical contact layer is unstructured.

5. The light-emitting diode according to claim 1, wherein the substrate is formed of GaAs and the light-generating layer is formed of InGaAlP.

6. The light-emitting diode according to claim 1, wherein the truncated elements are generated by an additional lithographic process step and subsequent dry etching.

7. The light-emitting diode according to claim 1, wherein

the surface of the semiconductor structure lying opposite the substrate is a rectangular surface with four corners;

the second electrical contact layer is formed by a cross structure with a central terminal surface and finger-shaped terminal surfaces proceeding therefrom in the direction toward the four corners of the rectangular surface;

regions of the rectangular surface between the finger-shaped terminal surfaces are covered with truncated elements.

8. The light-emitting diode according to claim 7, wherein the second electrical contact layer is opaque for the emitted light radiation.

9. The light-emitting diode according to claim 7, wherein the second electrical contact layer is formed by a transparent, thin, electrically conductive layer.

10. The light-emitting diode according to claim 9, wherein the electrically conductive layer is an indium tin oxide layer.

11. The light-emitting diode according to claim 1, wherein the second electrical contact layer is opaque for the emitted light radiation.

12. The light-emitting diode according to claim 1, wherein the second electrical layer is formed by a transparent electrically-conductive layer.

13. The light-emitting diode according to claim 12, wherein the electrically-conductive layer is an indium tin oxide layer.

14. A light-emitting diode comprising:

a semiconductor layer structure containing a substrate and at least one light-generating layer formed on the substrate,

a first electrical contact layer on the substrate and

a second electrical contact layer on at least one section of a surface of the semiconductor structure lying opposite the substrate,

the surface of the semiconductor structure lying opposite the substrate being structured over at least one section to have a plurality of three-sided truncated pyramids that are defined by the following parameter ranges;

15. The light-emitting diode according to claim 14, wherein V=1, φ

=75°

apply for all sidewalls, and the base area is an isosceles triangle with the principal angle θ

=70°

.

16. The light-emitting diode according to claim 14, wherein the surface of the semiconductor structure lying opposite the substrate is a rectangular surface with four corners, the second electrical contact layer is formed by a cross structure with a central terminal surface and finger-shaped terminal surfaces proceeding therefrom and in the direction toward the four corners, and the regions of the rectangular surface between the finger-shaped terminal surfaces are covered with truncated pyramids.

17. The light-emitting diode according to claim 16, wherein the second electrical contact layer is opaque for the emitted light radiation.

18. The light-emitting diode according to claim 16, wherein the second electrical contact layer is formed by a transparent, thin, electrically conductive layer of indium tin oxide.

19. The light-emitting diode according to claim 14, wherein the section of the surface lying opposite the substrate that is covered with the second electrical contact layer is unstructured.

20. The light emitting diode according to claim 14, wherein the truncated elements are generated by an additional lithographic process step and subsequent dry etching.