System and method for emitter layer shaping

• US 7,829,358 B2
• Filed: 02/06/2009
• Issued: 11/09/2010
• Est. Priority Date: 02/08/2008
• Status: Expired due to Fees

• Current Assignee: illumitex, Inc.
• Original Assignee: illumitex, Inc.
• Inventors: Winberg, Paul N., Duong, Dung T., Thomas, Matthew R., Khizar, Muhammad, Pickering, Elliot M.
• Primary Examiner(s): HOANG, QUOC DINH
• Application Number:
  US12/367,343
• Publication Number:
  US 20090289263A1
• Time in Patent Office: 641 Days
• Field of Search: 438/20, 438/317, 438/338, 438/342, 438/345, 257/13, 257/79, 257/164, 257/E21.05, 257/E21.379, 257/E21.381
• US Class Current: 438/20
• 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. A method of shaping an emitter layer of the LED, comprising:

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

determining a minimum height (h) of the miniature emitter utilizing the exit area (b) and the emitter area (a);

removing matter from an emitting material or growing the emitting material according to the first geometric configuration, the second geometric configuration, and the minimum height (h) to form a shaped portion having one or more miniature emitters meeting the minimum height (h); and

shaping sidewalls of the miniature emitters, 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 face with an angle of incidence at the exit face at less than or equal to a critical angle at the exit face.

2. The method according to claim 1, wherein removing matter from the emitting material further comprises:

patterning the emitting material using a first mask having the first geometric configuration;

etching the emitting material according to the minimum height (h) and the first geometric configuration;

patterning the emitting material using a second mask having the second geometric configuration; and

etching the emitting material according to the second geometric configuration.

3. The method according to claim 2, wherein the first mask defines a minimum width of etch channels in the emitter layer and wherein the one or more miniature emitters comprise an array of miniature emitters that are spaced apart by the minimum width of the etch channels.

4. The method according to claim 1, wherein the emitting material comprises gallium nitride (GaN).

5. The method according to claim 1, wherein removing matter from an emitting material or growing the emitting material by deposition according to the first geometric configuration, the second geometric configuration, and the minimum height (h) further forms an unshaped portion abutting a base substrate.

6. The method according to claim 5, wherein the base substrate comprises aluminum oxide (Al₂O₃) or silicon carbide (SiC).

7. The method according to claim 5, further comprising applying an anti-reflection coating on a surface of the base substrate, wherein the surface interfaces with air.

8. The method according to claim 1, wherein the first geometric configuration has four or six sides.

9. The method according to claim 1, wherein determining the minimum height (h) of the miniature emitter further comprises determining one or more limiting rays traversing a longest distance or approximately a longest distance from the emitter area (a) to the exit area (b) of the miniature emitter.

10. An LED manufactured by a method of shaping an emitter layer of the LED, the method comprising:

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

determining a minimum height (h) of the miniature emitter utilizing the exit area (b) and the emitter area (a);

removing matter from an emitting material or growing the emitting material according to the first geometric configuration, the second geometric configuration, and the minimum height (h) to form a shaped portion having one or more miniature emitters meeting the minimum height (h); and

shaping sidewalls of the miniature emitters, 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 face with an angle of incidence at the exit face at less than or equal to a critical angle at the exit face.

11. The LED of claim 10, wherein the emitter material comprises gallium nitride (GaN).

12. The LED of claim 10, wherein removing matter from an emitting material or growing the emitting material by deposition according to the first geometric configuration, the second geometric configuration, and the minimum height (h) further forms an unshaped portion abutting a base substrate.

13. The LED of claim 12, wherein the base substrate comprises aluminum oxide (Al₂O₃) or silicon carbide (SiC).

14. The LED of claim 12, wherein the method further comprises applying an anti-reflection coating on a surface of the base substrate, wherein the surface interfaces with air.

15. The LED of claim 10, wherein removing matter from the emitting material further comprises:

patterning the emitting layer using a first mask having the first geometric configuration;

etching the emitting layer according to the minimum height (h) and the first geometric configuration;

patterning the emitting layer using a second mask having the second geometric configuration; and

etching the emitting material according to the second geometric configuration.

16. The LED of claim 15, wherein the first mask defines a minimum width of etch channels in the emitter layer and wherein the one or more miniature emitters comprise an array of miniature emitters that are spaced apart by the minimum width of the etch channels.

17. The LED of claim 10, wherein the first geometric configuration has four or six sides.

18. The LED of claim 10, wherein determining the minimum height (h) of the miniature emitter further comprises determining one or more limiting rays traversing a longest distance or approximately a longest distance from the emitter area (a) to the exit area (b) of the miniature emitter.