Micro light-emitting element, micro light-emitting element array including the micro light-emitting element, and display device including the micro light-emitting element array
A micro light-emitting element includes a first conductivity type semiconductor layer including a lower surface on which an uneven pattern is formed, an active layer provided on the first conductivity type semiconductor layer, a second conductivity type semiconductor layer provided on the active layer, at least one electrode provided on the second conductivity type semiconductor layer, and a transparent coating layer including a first surface covering the lower surface of the first conductivity type semiconductor layer, and a second surface facing the first surface and having a second surface roughness that is less than a first surface roughness of the lower surface of the first conductivity type semiconductor layer.
1. A micro light-emitting element comprising:
a first conductivity type semiconductor layer including a lower surface on which an uneven pattern is formed, the lower surface of the first conductivity type semiconductor layer having a first surface roughness;
an active layer provided on the first conductivity type semiconductor layer;
a second conductivity type semiconductor layer provided on the active layer;
at least one electrode provided on the second conductivity type semiconductor layer; and
a transparent coating layer including a first surface covering the lower surface of the first conductivity type semiconductor layer, and a second surface on an opposite side of the first surface, the second surface having a second surface roughness that is less than the first surface roughness,
wherein the transparent coating layer is an outermost layer of the micro light-emitting element.
2. The micro light-emitting element of claim 1 , wherein the second surface roughness is 5 nm or less.
3. The micro light-emitting element of claim 1 , wherein the transparent coating layer includes one of polyimide (PI), spin-on-glass (SOG), photoresist, silicon oxide, or silicon nitride.
4. The micro light-emitting element of claim 1 , wherein the transparent coating layer has a light transmittance of 80% or more.
5. The micro light-emitting element of claim 1 , wherein the transparent coating layer has a refractive index value between 1 and 2.
6. The micro light-emitting element of claim 1 , wherein the first conductivity type semiconductor layer, the active layer, and the second conductivity type semiconductor layer each include one of GaN, InN, AlN, InGaN, AlGaN, InAlGaN, AlInN, AlGaAs, InGaAs, AlInGaAs, GaP, AlGaP, InGaP, AlInGaP, or InP.
7. The micro light-emitting element of claim 1 , wherein a first electrode and a second electrode are provided on the second conductivity type semiconductor layer, and wherein the first electrode and the second electrode are spaced apart from each other.
8. The micro light-emitting element of claim 7 , wherein the first electrode has a ring shape corresponding to an edge of the upper surface of the second conductivity type semiconductor layer, and
wherein the second electrode is surrounded by the first electrode.
9. The micro light-emitting element of claim 1 , wherein at least one of a plurality of nanobeads or a plurality of nanopores are formed inside the transparent coating layer.
10. The micro light-emitting element of claim 1 , wherein an engraved nano-pattern is formed on the second surface of the transparent coating layer.
11. The micro light-emitting element of claim 1 , wherein a cross-section of the transparent coating layer is a rectangular shape and an entirety of the first surface of the transparent coating layer facing the first conductivity type semiconductor layer contacts the first conductivity type semiconductor layer.
12. A micro light-emitting element comprising:
a first conductivity type semiconductor layer including a lower surface on which an uneven pattern is formed, the lower surface of the first conductivity type semiconductor layer having a first surface roughness;
an active layer provided on the first conductivity type semiconductor layer;
a second conductivity type semiconductor layer provided on the active layer;
at least one electrode provided on the second conductivity type semiconductor layer; and
a transparent coating layer including a first surface covering an upper surface of the second conductivity type semiconductor layer, and a second surface on an opposite side of the first surface, the second surface having a second surface roughness that is less than the first surface roughness,
wherein the transparent coating layer is an outermost layer of the micro light-emitting element.
13. The micro light-emitting element of claim 12 , wherein a hole exposing at least a portion of the at least one electrode is formed in the second surface.
14. The micro light-emitting element of claim 12 , wherein the transparent coating layer has a first thickness that is greater than a second thickness of the at least one electrode.
15. The micro light-emitting element of claim 11 , wherein the second surface roughness is 5 nm or less.
16. A micro light-emitting element array comprising:
a plurality of micro light-emitting elements, each of the plurality of micro light-emitting elements comprising:
a micro light-emitting structure including a first surface on which an electrode is provided, and a second surface facing the first surface, the second surface including an uneven pattern having a first surface roughness, and
a transparent coating layer including a third surface covering the second surface, and a fourth surface on an opposite side of the third surface, the fourth surface having a second surface roughness that is less than the first surface roughness, wherein the transparent coating layer is an outermost layer of the micro light-emitting element; and
a substrate including an upper surface having a first region in which the plurality of micro light-emitting elements are provided and a second region surrounding the first region.
17. The micro light-emitting element array of claim 16 , wherein the second surface roughness is 5 nm or less.
18. The micro light-emitting element array of claim 16 , wherein the micro light-emitting structure included in each of the plurality of micro light-emitting elements includes a structure in which a first conductivity type semiconductor layer, an active layer, and a second conductivity type semiconductor layer are sequentially stacked, and
wherein the first surface of the micro light-emitting structure is an upper surface of the second conductivity type semiconductor layer, and the second surface of the micro light-emitting structure is a lower surface of the first conductivity type semiconductor layer.
19. The micro light-emitting element array of claim 16 , wherein the substrate includes a transfer substrate including a plurality of grooves formed in the upper surface of the substrate, and
each of the plurality of micro light-emitting elements is arranged so that the first surface of the micro light-emitting structure faces an upper opening of the plurality of grooves, and the fourth surface of the transparent coating layer is in contact with bottoms of the plurality of grooves.
20. The micro light-emitting element array of claim 16 , wherein the substrate includes a transfer substrate including a plurality of hydrophilic regions formed on the upper surface of the substrate and a hydrophobic region surrounding the plurality of hydrophilic regions, and
wherein each of the plurality of micro light-emitting elements is arranged so that the fourth surface of the transparent coating layer is in contact with the plurality of hydrophilic regions.
21. The micro light-emitting element array of claim 16 , wherein the substrate includes a driving circuit board including a plurality of grooves formed in the upper surface of the substrate and a plurality of electrode structures respectively provided in the plurality of grooves, and
wherein each of the plurality of micro light-emitting elements is arranged so that the electrode of each of the plurality of micro light-emitting elements provided on the first surface are respectively in contact with the plurality of electrode structures provided in the plurality of grooves, and the fourth surface faces upper openings of the plurality of grooves.
22. The micro light-emitting element array of claim 16 , wherein the substrate includes a driving circuit board including a plurality of electrode structures respectively provided in a plurality of element regions separated from each other on the upper surface thereof, and
wherein each of the plurality of micro light-emitting elements is arranged so that the electrode of each of the plurality of micro light-emitting elements provided on the first surface is in contact with the plurality of electrode structures provided in the plurality of element regions.
23. A micro light-emitting element array comprising:
a plurality of micro light-emitting elements, each of the plurality of micro light-emitting elements comprising:
a micro light-emitting structure including a first surface on which an electrode is provided and a second surface facing the first surface, the second surface including an uneven pattern having a first surface roughness, and
a transparent coating layer including a third surface covering the first surface and a fourth surface on an opposite side of the third surface, the fourth surface having a second surface roughness that is less than the first surface roughness, wherein the transparent coating layer is an outermost layer of the micro light-emitting element; and
a substrate including an upper surface having a first region in which the plurality of micro light-emitting elements are provided and a second region surrounding the first region.
24. The micro light-emitting element array of claim 23 , wherein a hole exposing at least a portion of the electrode is formed in the fourth surface.
25. The micro light-emitting element array of claim 23 , wherein the substrate includes a driving circuit board including a plurality of grooves formed in the upper surface of the substrate and a plurality of electrode structures provided in the plurality of grooves, and
wherein each of the plurality of micro light-emitting elements is arranged so that the fourth surface faces the plurality of electrode structures provided in the plurality of grooves and the second surface faces upper openings of the plurality of grooves.
26. The micro light-emitting element array of claim 23 , wherein the substrate includes a driving circuit board including a plurality of hydrophilic regions formed on the upper surface of the substrate, a hydrophobic region surrounding the plurality of hydrophilic regions, and a plurality of electrode structures provided in the plurality of hydrophilic regions, and
wherein each of the plurality of micro light-emitting elements is arranged so that the fourth surface faces the plurality of electrode structures provided in the plurality of hydrophilic regions.
27. A display device comprising:
a pixel array including a plurality of micro light-emitting elements;
a driving circuit configured to drive the pixel array; and
a processor configured to control the operation of the driving circuit;
wherein each of the plurality of micro light-emitting elements comprises:
a first conductivity type semiconductor layer including a lower surface on which an uneven pattern is formed, the lower surface of the first conductivity type semiconductor layer having a first surface roughness;
an active layer provided on the first conductivity type semiconductor layer;
a second conductivity type semiconductor layer provided on the active layer;
at least one electrode provided on the second conductivity type semiconductor layer; and
a transparent coating layer including a first surface covering the lower surface of the first conductivity type semiconductor layer, and a second surface on an opposite side of the first surface, the second surface having a second surface roughness that is less than the first surface roughness, wherein the transparent coating layer is an outermost layer of the micro light-emitting element.
28. The display device of claim 27 , wherein the second surface roughness is 5 nm or less.
29. A display device comprising:
a pixel array including a plurality of micro light-emitting elements;
a driving circuit configured to drive the pixel array; and
a processor configured to control the operation of the driving circuit;
wherein each of the plurality of micro light-emitting element comprises:
a first conductivity type semiconductor layer including a lower surface on which an uneven pattern is formed, the lower surface of the first conductivity type semiconductor layer having a first surface roughness;
an active layer provided on the first conductivity type semiconductor layer;
a second conductivity type semiconductor layer provided on the active layer;
at least one electrode provided on the second conductivity type semiconductor layer; and
a transparent coating layer including a first surface covering an upper surface of the second conductivity type semiconductor layer, and a second surface on an opposite side of the third surface, the fourth surface having a second surface roughness that is less than the first surface roughness,
wherein the transparent coating layer is an outermost layer of the micro light-emitting element.
30. A micro light-emitting element comprising:
a first conductivity type semiconductor layer including a lower surface on which an uneven pattern is formed, the lower surface of the first conductivity type semiconductor layer having a first characteristic configured to apply a first Van der Waals force;
an active layer provided on the first conductivity type semiconductor layer;
a second conductivity type semiconductor layer provided on the active layer;
at least one electrode provided on the second conductivity type semiconductor layer; and
a transparent coating layer including:
a first surface covering one of the lower surface of the first conductivity type semiconductor layer or an upper surface of the second conductivity type semiconductor layer, and
a second surface having a second characteristic configured to apply a second Van der Waals force greater than the first Van der Waals force,
wherein the transparent coating layer is an outermost layer of the micro light-emitting element.
31. The micro light-emitting element of claim 30 , wherein the first characteristic is a first surface roughness of the lower surface of the first conductivity type semiconductor layer, and the second characteristic is a second surface roughness of the second surface of the transparent coating layer.