System and method for emitter layer shaping

• US 8,263,993 B2
• Filed: 06/07/2010
• Issued: 09/11/2012
• Est. Priority Date: 02/08/2008
• Status: Expired due to Fees

• Current Assignee: illumitex, Inc.
• Original Assignee: illumitex, Inc.
• Inventors: Duong, Dung T., Winberg, Paul N., Thomas, Matthew R., Pickering, Elliot M., Khizar, Muhammad
• Primary Examiner(s): Hoang, Quoc
• Application Number:
  US12/795,484
• Publication Number:
  US 20100270560A1
• Time in Patent Office: 827 Days
• Field of Search: 257/98, 257/99
• US Class Current: 257/98
• 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
• CPC Class Codes: H01L 33/20 with a particular shape, e.g. curved or truncated substrate
• CPC Class Codes: H01L 33/32 containing nitrogen

Abstract

Embodiments of an LED disclosed has an emitter layer shaped to a controlled depth or height relative to a substrate of the LED to maximize the light output of the LED and to achieve a desired intensity distribution. In some embodiments, the exit face of the LED may be selected to conserve radiance. In some embodiments, shaping the entire LED, including the substrate and sidewalls, or shaping the substrate alone can extract 100% or approximately 100% of the light generated at the emitter layers from the emitter layers. In some embodiments, the total efficiency is at least 90% or above. In some embodiments, the emitter layer can be shaped by etching, mechanical shaping, or a combination of various shaping methods. In some embodiments, only a portion of the emitter layer is shaped to form the tiny emitters. The unshaped portion forms a continuous electrical connection for the LED.

Claims

1. An LED, comprising:

a base substrate; and

an emitter layer on a surface of the substrate configured to emit light in an emission half angle, wherein the emitter layer has a shaped portion comprising;

an emitter area;

an exit area a height from the emitter area;

sidewalls running from the emitter area to the exit area, wherein each of the sidewalls comprises a plurality of areas at different angles relative to the emitter area and wherein each sidewall is positioned and shaped to cause at least a majority of rays having a straight transmission path from the emitter area to that sidewall to reflect to the exit area with an angle of incidence at the exit area at less than or equal to a critical angle at an emitter layer to substrate boundary; and

wherein the size of the exit area and shapes of the sidewalls are configured so that at least 60% of the light generated in the emitter layer exits the emitter layer into the substrate in the emission half angle.

2. The LED of claim 1, wherein the emitter layer further comprises an unshaped portion abutting the substrate.

3. The LED of claim 1, wherein the emitter layer comprises gallium nitride (GaN).

4. The LED of claim 1, wherein the substrate comprises aluminum oxide (Al₂O₃) or silicon carbide (SiC).

5. The LED of claim 1, wherein the emitting area and exit area comprise different sizes of squares, rectangles, or hexagons.

6. The LED of claim 1, wherein the emitter layer comprises an array of emitters each having an exit area (b), an emitter area (a), a minimum height (h), and sidewalls.

7. The LED of claim 1, wherein the shaped portion of the emitter layer is shaped to achieve at least 75% light extraction from the LED.

8. An LED array comprising:

one or more sections of substrate;

an array of emitter layers coupled to the one or more sections of substrate, wherein each emitter layer has a shaped portion comprising;

an emitter area;

an exit area a height from the emitter area;

sidewalls running from the emitter area to the exit area, wherein each of the sidewalls comprises a plurality of areas at different angles relative to the emitter area and wherein the plurality of areas are positioned and shaped to cause at least a majority of rays having a straight transmission path from the emitter area to that sidewall to reflect to the exit area with an angle of incidence at an exit face at less than or equal to a critical angle at the exit face and wherein the shapes of the sidewalls and the size of the exit area are selected so that at least 60% of the light generated in the emitter layer exits the exit face into the substrate in a selected half angle.

9. The LED array of claim 8, wherein a single section of substrate is the substrate of multiple LEDs in the LED array.

10. The LED array of claim 9, wherein the emitter layer further comprises an unshaped portion abutting the substrate.

11. The LED array of claim 9, wherein each emitter layer comprises gallium nitride (GaN).

12. The LED array of claim 9, wherein the one or more sections of substrate comprise aluminum oxide (Al₂O₃) or silicon carbide (SiC).

13. The LED array of claim 9, wherein for each emitting layer, the emitting area and exit face comprise different sizes of squares, rectangles, or hexagons.

14. The LED array of claim 9, wherein the shaped portion of the emitter layer is shaped to achieve at least 75% light extraction from the LED.

15. An LED, comprising:

a base substrate; and

an emitter layer on a surface of the base substrate, wherein the emitter layer has a shaped portion, wherein the shaped portion comprises;

an emitter area (a);

an exit area (b) a height (h) from the emitter area;

sidewalls, wherein each sidewall comprises a plurality of areas at different angles relative to the emitter area (a); and

wherein the exit area (b) has an exit face in a first geometric configuration, wherein the emitter area (a) has a quantum well region in a second geometric configuration;

wherein the height (h) is selected such that all rays having a direct transmission path to a sidewall are incident on that sidewall at less than or equal to a critical angle at that sidewall;

wherein each of the sidewalls is positioned and shaped to cause at least a majority of rays having a straight transmission path from the emitter area to that sidewall to reflect to the exit face with an angle of incidence at the exit face at less than or equal to a critical angle at the exit face.

16. The LED of claim 15, wherein the emitter layer further comprises an unshaped portion abutting the base substrate.

17. The LED of claim 15, wherein the emitter layer comprises gallium nitride (GaN).

18. The LED of claim 15, wherein the base substrate comprises aluminum oxide (Al₂O₃) or silicon carbide (SiC).

19. The LED of claim 15, wherein the first and the second geometric configurations comprise different sizes of squares, rectangles, or hexagons.

20. The LED of claim 15, wherein the emitter layer comprises an array of emitters each having an exit area (b), an emitter area (a), a minimum height (h), and sidewalls.

21. The LED of claim 15, wherein the shaped portion of the emitter layer is shaped to achieve at least 75% light extraction from the LED.