High density pixelated-LED chips and chip array devices

• US 10,734,363 B2
• Filed: 10/30/2018
• Issued: 08/04/2020
• Est. Priority Date: 08/03/2017
• Status: Active Grant

• Current Assignee: Creeled Incorporated
• Original Assignee: CREE Incorporated (Wolfspeed, Inc.)
• Inventors: Andrews, Peter Scott
• Primary Examiner(s): Sarkar, Asok K
• Application Number:
  US16/174,584
• Publication Number:
  US 20190074266A1
• Time in Patent Office: 644 Days
• Field of Search: None
• CPC Class Codes: H01L 23/60 Protection against electrostatic charges or discharges, e.g. Faraday shields
• CPC Class Codes: H01L 25/0753 the devices being arranged next to each other
• CPC Class Codes: H01L 27/156 two-dimensional arrays
• CPC Class Codes: H01L 2933/0083 Periodic patterns for optical field-shaping in or on the semiconductor body or semiconductor body package, e.g. photonic bandgap structures
• 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
• CPC Class Codes: H01L 33/46 Reflective coating, e.g. dielectric Bragg reflector
• CPC Class Codes: H01L 33/60 Reflective elements
• CPC Class Codes: H01L 33/62 Arrangements for conducting electric current to or from the semiconductor body, e.g. lead-frames, wire-bonds or solder balls

Abstract

Pixelated-LED chips and related methods are disclosed. A pixelated-LED chip includes an active layer with independently electrically accessible active layer portions arranged on or over a light-transmissive substrate. The active layer portions are configured to illuminate different light-transmissive substrate portions to form pixels. Various enhancements may beneficially provide increased contrast (i.e., reduced cross-talk between pixels) and/or promote inter-pixel illumination homogeneity, without unduly restricting light utilization efficiency. In some aspects, a light extraction surface of each substrate portion includes protruding features and light extraction surface recesses. Lateral borders between different pixels are aligned with selected light extraction surface recesses. In some aspects, selected light extraction surface recesses extend through an entire thickness of the substrate. Other technical benefits may additionally or alternatively be achieved.

Claims

1. A pixelated-LED chip comprising:

an active layer comprising a plurality of active layer portions;

a plurality of substrate portions supporting the plurality of active layer portions, wherein each substrate portion comprises a light-transmissive material, a light injection surface, and a light extraction surface, wherein the light injection surface is arranged between the active layer and the light extraction surface; and

a plurality of anode-cathode pairs associated with the plurality of active layer portions;

wherein each active layer portion of the plurality of active layer portions comprises a different anode-cathode pair of the plurality of anode-cathode pairs and is configured to illuminate a different substrate portion of the plurality of substrate portions and transmit light through the light extraction surface of the substrate portion, such that the plurality of active layer portions and the plurality of substrate portions form a plurality of pixels;

wherein the light extraction surface of each substrate portion comprises a plurality of protruding features and a plurality of light extraction surface recesses, and each protruding feature of the plurality of protruding features is separated from at least one other protruding feature by a light extraction surface recess of the plurality of light extraction surface recesses; and

wherein lateral borders between different pixels of the plurality of pixels are aligned with selected light extraction surface recesses of the plurality of light extraction surface recesses.

2. The pixelated-LED chip of claim 1, wherein the lateral borders between different pixels of the plurality of pixels are aligned with selected light extraction surface recesses of the plurality of light extraction surface recesses that extend through an entire thickness of the substrate portions.

3. The pixelated-LED chip of claim 1, wherein the plurality of protruding features comprises a first group of protruding features comprising a first size including at least one of height, width, or length, and comprises a second group of protruding features comprising a second size including at least one of height, width, or length, wherein the second size differs from the first size.

4. The pixelated-LED chip of claim 1, wherein the plurality of protruding features comprises a first group of protruding features comprising a first shape, and comprises a second group of protruding features comprising a second shape, wherein the second shape differs from the first shape.

5. The pixelated-LED chip of claim 1, wherein each protruding feature of the plurality of protruding features comprises a polyhedral or truncated polyhedral shape with a plurality of inclined lateral faces, and each inclined lateral face of the plurality of inclined lateral faces comprises an angle of inclination from vertical in a range of from about fifteen degrees to about forty-five degrees.

6. The pixelated-LED chip of claim 1, wherein each protruding feature of the plurality of protruding features comprises a maximum width of from about one fifth to about one half of a maximum width of a pixel of the plurality of pixels with which each protruding feature is associated.

7. The pixelated-LED chip of claim 1, wherein:

the plurality of substrate portions comprises a plurality of lateral edges;

the plurality of protruding features comprises a first group of protruding features positioned adjacent to at least some lateral edges of the plurality of lateral edges, and comprises a second group of protruding features positioned distal from the plurality of lateral edges; and

at least some protruding features of the first group of protruding features differ in at least one of (a) size, (b) shape, (c) number, or (d) distribution relative to at least some protruding features of the second group of protruding features.

8. The pixelated-LED chip of claim 1, wherein:

the plurality of substrate portions comprises a plurality of corners;

the plurality of protruding features comprises a first group of protruding features positioned adjacent to the plurality of corners, and comprises a second group of protruding features positioned distal from the plurality of corners; and

at least some protruding features of the first group of protruding features differ in at least one of (a) size, (b) shape, (c) number, or (d) distribution relative to at least some protruding features of the second group of protruding features.

9. The pixelated-LED chip of claim 1, further comprising at least one lumiphoric material arranged on or over the plurality of protruding features, wherein the at least one lumiphoric material is configured to receive at least a portion of light emitted by the plurality of active layer portions and to responsively generate lumiphor emissions.

10. The pixelated-LED chip of claim 9, wherein lumiphoric material associated with at least one first pixel of the plurality of pixels differs with respect to at least one of (a) composition, (b) concentration, (c) particle size, or (d) distribution relative to lumiphoric material associated with at least one second pixel of the plurality of pixels.

11. The pixelated-LED chip of claim 1, wherein the plurality of substrate portions comprises silicon carbide, and the plurality of active layer portions comprises at least one Group III nitride material.

12. A pixelated-LED chip comprising:

an active layer comprising a plurality of active layer portions;

a plurality of substrate portions supporting the plurality of active layer portions, wherein each substrate portion comprises a light-transmissive material, a light injection surface, and a light extraction surface, wherein the light injection surface is arranged between the active layer and the light extraction surface; and

a plurality of anode-cathode pairs associated with the plurality of active layer portions;

wherein each active layer portion of the plurality of active layer portions comprises a different anode-cathode pair of the plurality of anode-cathode pairs and is configured to illuminate a different substrate portion of the plurality of substrate portions and transmit light through the light extraction surface of the substrate portion, such that the plurality of active layer portions and the plurality of substrate portions form a plurality of pixels;

wherein at least one substrate portion of the plurality of substrate portions comprises;

a first protruding feature comprising a first angle between two opposing faces; and

a second protruding feature comprising a second angle between two opposing faces, wherein the second angle is larger than the first angle.

13. The pixelated-LED chip of claim 12, wherein the second angle exceeds the first angle by at least fifteen degrees.

14. The pixelated-LED chip of claim 13, wherein the second angle is about ninety degrees and the first angle is about sixty degrees.

15. The pixelated-LED chip of claim 12, wherein the second protruding feature is closer to a pixel sidewall than the first protruding feature.

16. The pixelated-LED chip of claim 12, wherein the first protruding feature and the second protruding feature comprise silicon carbide.

17. A pixelated-LED chip comprising:

an active layer comprising a plurality of active layer portions;

a plurality of substrate portions supporting the plurality of active layer portions, wherein each substrate portion comprises a light-transmissive material, a light injection surface, and a light extraction surface, wherein the light injection surface is arranged between the active layer and the light extraction surface; and

a plurality of anode-cathode pairs associated with the plurality of active layer portions;

wherein each active layer portion of the plurality of active layer portions comprises a different anode-cathode pair of the plurality of anode-cathode pairs and is configured to illuminate a different substrate portion of the plurality of substrate portions and transmit light through the light extraction surface of the substrate portion, such that the plurality of active layer portions and the plurality of substrate portions form a plurality of pixels;

wherein the light extraction surface of each substrate portion comprises a light extraction surface recess between pixel sidewalls of the plurality of pixels; and

the pixelated-LED chip further comprises a reflective layer on the pixel sidewalls.

18. The pixelated-LED chip of claim 17, wherein the reflective layer comprises at least one of a metal reflector, a dielectric reflector, or a metal reflector in combination with a dielectric reflector.

19. A pixelated-LED chip comprising:

an active layer comprising a plurality of active layer portions;

a substrate comprising a plurality of substrate portions supporting the plurality of active layer portions, wherein each substrate portion of the plurality of substrate portions comprises a light extraction surface; and

a plurality of anode-cathode pairs associated with the plurality of active layer portions;

wherein each active layer portion of the plurality of active layer portions comprises a different anode-cathode pair of the plurality of anode-cathode pairs and is configured to illuminate a different substrate portion of the plurality of substrate portions and transmit light through the light extraction surface of the substrate portion, such that the plurality of active layer portions and the plurality of substrate portions form a plurality of pixels;

wherein the light extraction surface of each substrate portion comprises at least one first light extraction surface recess and at least one second light extraction surface recess; and

wherein the at least one second light extraction surface recess is aligned with a street between adjacent pixels of the plurality of pixels; and

the pixelated-LED chip includes at least one of the following features (i) or (ii);

(i) the at least one first light extraction surface recess extends deeper into the substrate than the at least one second light extraction surface recess, or (ii) the second light extraction surface recess comprises a wider bottom than the first light extraction surface recess.

20. The pixelated-LED chip of claim 19, wherein the at least one first light extraction surface recess extends deeper into the substrate than the at least one second light extraction surface recess.

21. The pixelated-LED chip of claim 19, wherein the second light extraction surface recess comprises a wider bottom than the first light extraction surface recess.