LED system and method

• US 8,087,960 B2
• Filed: 10/01/2007
• Issued: 01/03/2012
• Est. Priority Date: 10/02/2006
• 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.
• Primary Examiner(s): Patel, Nimeshkumar
• Assistant Examiner(s): Bowman, Mary Ellen
• Application Number:
  US11/906,219
• Publication Number:
  US 20080081531A1
• Time in Patent Office: 1,555 Days
• Field of Search: 216/24, 257/79, 257/98, 362/84, 359/603, 438/745, 451/36, 445/3
• US Class Current: 445/3
• CPC Class Codes: H01L 33/10 with a light reflecting structure, e.g. semiconductor Bragg reflector
• CPC Class Codes: H01L 33/20 with a particular shape, e.g. curved or truncated substrate
• CPC Class Codes: H01L 33/44 characterised by the coatings, e.g. passivation layer or anti-reflective coating

Abstract

Embodiments provide an LED comprising a quantum well region operable to generate light and a substrate having an interface with the quantum well region, wherein light generated by the quantum well region traverses the interface to enter the substrate and exit the LED through an exit face of the substrate. The exit face may be opposite from and a distance from the interface, with some portion or all of this LED being shaped to optimize the light extraction efficiency of the device. The exit face can have at least 70% of a minimum area necessary to conserve brightness for a desired half-angle of light. Sidewalls of the LED may be positioned and shaped so that rays incident on a sidewall 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.

Claims

1. A method of manufacturing an LED comprising:

determining a size of an exit face of a shaped substrate portion of the LED so that the exit face has at least 70% of a minimum area necessary to conserve radiance for a desired half-angle of light projected from the LED;

determining a distance between the exit face and an interface between the shaped substrate portion and a quantum well region of the LED;

determining shapes and positions of a set of sidewalls of the shaped substrate portion of the LED so that each sidewall is positioned and shaped to cause at least a majority of rays having a straight transmission path from the interface to that sidewall to reflect through total internal reflection 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; and

forming the shaped substrate portion of the LED in accordance with the determined size of the exit face, shapes and positions of the set of sidewalls and distance between the exit face and the interface;

wherein the method is performed by performing steps in the order of;

(a) determining boundary conditions for the shaped substrate portion of the LED, wherein the boundary conditions comprise the size of the exit face of the shaped substrate portion of the LED and the distance between the exit face and the interface between the shaped substrate portion and the quantum well region of the LED;

(b) the determining the shapes and positions of the set of sidewalls of the shaped substrate portion of the LED; and

(c) the forming the shaped substrate portion of the LED.

2. The method of claim 1, depositing one or more layers on the shaped substrate portion to form the quantum well region of the LED after the shaped substrate portion has been formed.

3. The method of claim 1, further comprising:

providing a substrate and one or more layers for a quantum well region of the LED;

removing material from the substrate to form the shaped substrate portion of the LED.

4. The method of claim 3, wherein removing material from the substrate further comprises removing material using one of an ultrasonic removal process;

laser ablation or water jet cutting.

5. The method of claim 3, wherein removing material from the substrate further comprises cutting or grinding the substrate with a blade having an inverse shape to a desired shape of the shaped substrate portion of the LED.

6. The method of claim 3, wherein removing material from the substrate further comprises etching the substrate.

7. The method of claim 3, further comprising coating the substrate with a photo-luminescent layer prior to removing material from the substrate.

8. The method of claim 1, further comprising shaping the quantum well region of the LED in conjunction with shaping the substrate.

9. The method of claim 1, wherein the LED is shaped to achieve a desired light output profile.

10. The method of claim 1, wherein the size of the exit face is selected to have at least the minimum area necessary to conserve radiance.

11. A method of shaping an LED comprising:

providing a wafer comprising a substrate and one or more layers for a quantum well region of the LED;

grinding the substrate to form a shaped substrate portion of the LED;

wherein the shaped substrate portion is shaped to comprise;

an exit face opposite from and a distance from an interface with the to receive light generated by a quantum well region of the LED, the exit face having a size being at least 70% of a minimum area necessary to conserve radiance for a desired half-angle of light projected from the shaped substrate; and

a set of sidewalls, wherein each sidewall is positioned and shaped so that at least a majority of rays having a straight transmission path from the interface to that sidewall reflect through total internal reflection to the exit face with an angle of incidence at the exit face of less than or equal to a critical angle at the exit face;

wherein the method is performed by performing steps in the order of;

(a) determining boundary conditions for the shaped substrate portion of the LED, wherein the boundary conditions comprise the size of the exit face of the shaped substrate portion of the LED and the distance between the exit face and the interface between the shaped substrate portion and the quantum well region of the LED;

(b) determining the shapes and positions of the set of sidewalls of the shaped substrate portion of the LED; and

(c) shaping the shaped substrate portion of the LED.

12. The method of claim 11, wherein grinding the substrate comprises grinding the substrate with a shaped diamond grinding wheel.

13. The method of claim 11, wherein grinding the substrate comprises:

making multiple cuts in the substrate along a first axis at least part way through the wafer; and

making multiple cuts in the substrate along a second axis at least part way through the wafer at an angle to the first axis to create shaped substrate portions for multiple LEDs.

14. The method of claim 11, further comprising shaping the quantum well region of the LED in conjunction with shaping the substrate.

15. The method of claim 11, wherein the LED is shaped to achieve a desired light output profile.

16. The method of claim 11, wherein the exit face has the minimum area necessary to conserve radiance.

17. A method of shaping an LED comprising:

providing a wafer comprising a substrate and one or more layers for a quantum well region of the LED;

etching the substrate to form a shaped substrate portion of the LED;

wherein the shaped substrate portion of the LED is shaped to comprise;

an exit face opposite and at a distance from an interface to receive light generated by a quantum well region of the LED, the exit face having at least 70% of a minimum area necessary to conserve radiance for a desired half-angle of light projected from the shaped substrate portion of the LED; and

a set of sidewalls, wherein each sidewall is positioned and shaped so that at least a majority of rays having a straight transmission path from the interface to that sidewall reflect through total internal reflection to the exit face with an angle of incidence at the exit face of less than or equal to a critical angle at the exit face;

wherein the method is performed by performing steps in the order of;

(a) determining boundary conditions for the shaped substrate portion of the LED, wherein the boundary conditions comprise the size of the exit face of the shaped substrate portion of the LED and the distance between the exit face and the interface between the shaped substrate portion and the quantum well region of the LED;

(b) determining the shapes and positions of the set of sidewalls of the shaped substrate portion of the LED; and

(c) shaping the shaped substrate portion of the LED.

18. The method of claim 17, wherein etching the substrate further comprises dry etching the substrate.

19. The method of claim 17, wherein etching the substrate further comprises wet etching the substrate.

20. The method of claim 17, wherein etching the substrate further comprises etching the substrate using a multiple etch resist etching process.

21. The method of claim 17, further comprising shaping the quantum well region of the LED in conjunction with shaping the substrate.

22. The method of claim 17, wherein the LED is shaped to achieve a desired light output profile.

23. The method of claim 17, wherein the exit face is shaped to have at least the minimum area necessary to conserve radiance.

24. A method of manufacturing an LED comprising:

providing a substrate and one or more layers for a quantum well region of the LED;

removing material from the substrate to form a shaped substrate portion of the LED, the shaped substrate portion comprising;

two or more exit faces having a size such that a combined area of the two or more exit faces being at least 70% of a minimum area necessary to conserve radiance for a desired half-angle of light projected from the LED; and

a set of sidewalls, wherein each sidewall is positioned and shaped so that at least a majority of rays having a straight transmission path from an interface to that sidewall reflect through total internal reflection to an exit face of the two or more exit faces with an angle of incidence at that exit face of less than or equal to a critical angle at that exit face;

wherein the method is performed by performing steps in the order of;

(a) determining boundary conditions for the shaped substrate portion of the LED, wherein the boundary conditions comprise the size of the two or more exit faces of the shaped substrate portion of the LED and the distance between the two or more exit faces and the interface between the shaped substrate portion and the quantum well region of the LED;

(b) determining the shapes and positions of the set of sidewalls of the shaped substrate portion of the LED; and

(c) shaping the substrate portion of the LED.

25. The method of claim 24, wherein the two or more exit faces have an area that is at least the minimum area necessary to conserve radiance.