MICRO LIGHT-EMITTING DIODE (LED) STRUCTURE
The present disclosure provides structures for a micro light-emitting diode (LED) array, to improve light extraction efficiency. An exemplary structure includes: a bottom epitaxial layer of a first conductive type, continuously formed across the micro LED array; a light-emitting layer, formed on the bottom epitaxial layer and continuously formed across the micro LED array; a top epitaxial layer of a second conductive type, wherein the top epitaxial layer is formed on the light-emitting layer and continuously formed across the micro LED array; and a first trench, formed in the top epitaxial layer and between adjacent micro LED.
1 . A micro light-emitting diode (LED) structure for an array of micro LEDs, wherein the micro LED structure comprises:
a bottom epitaxial layer of a first conductive type, continuously formed across the micro LED array;
a light-emitting layer, formed on the bottom epitaxial layer and continuously formed across the micro LED array;
a top epitaxial layer of a second conductive type, wherein the top epitaxial layer is formed on the light-emitting layer and continuously formed across the micro LED array; and
a first trench, formed in the top epitaxial layer and between adjacent micro LEDs.
2 . The micro LED structure according to claim 1 , further comprising a second trench, formed in the bottom epitaxial layer and between adjacent micro LEDs, wherein the second trench is continuously formed across the micro LED array.
3 . The micro LED structure according to claim 2 , wherein a top of the second trench is not higher than a top of the bottom epitaxial layer.
4 . The micro LED structure according to claim 1 , wherein a bottom of the first trench is not lower than a bottom of the top epitaxial layer.
5 . The micro LED structure according to claim 1 , further comprising:
a top conductive layer, formed on the top epitaxial layer;
a bottom conductive structure, formed below the bottom epitaxial layer; and
a top-connected structure, formed in the first trench and between adjacent micro LEDs.
6 . The micro LED structure according to claim 5 , wherein the first trench is continuously formed across the micro LED array, and the top-connected structure is continuously formed in the first trench and across the micro LED array.
7 . The micro LED structure according to claim 6 , wherein the top-connected structure forms a closed shape around the micro LED array.
8 . The micro LED structure according to claim 5 , wherein a top of the top-connected structure is not lower than atop of the top epitaxial layer.
9 . The micro LED structure according to claim 5 , wherein the top-connected structure comprises a conductive material and forms an ohmic contact with the top conductive layer.
10 . The micro LED structure according to claim 9 , wherein the conductive material of the top-connected structure is metal.
11 . The micro LED structure according to claim 5 , further comprising an array of top contacts, formed between the top epitaxial layer and the top conductive layer.
12 . The micro LED structure according to claim 11 , wherein:
the array of top contacts comprises a conductive material and forms an ohmic contact with the top conductive layer; and
the array of top contacts is respectively located at centers of the array of micro LEDs.
13 . The micro LED structure according to claim 11 , wherein the top-connected structure and the array of top contacts comprise a same conductive material.
14 . The micro LED structure according to claim 1 , further comprising an array of micro lenses formed above the top epitaxial layer.
15 . The micro LED structure according to claim 5 , further comprising an array of micro lenses formed on the top conductive layer, wherein gaps are formed between adjacent micro lenses to expose the top-connected structure to air.
16 . The micro LED structure according to claim 14 , wherein each of the micro lenses comprises a top hemisphere lens and a bottom spacer below the top hemisphere lens.
17 . The micro LED structure according to claim 16 , wherein a width of the bottom spacer is greater than a diameter of the top hemisphere lens.
18 . The micro LED structure according to claim 16 , wherein a height of the bottom spacer is determined based on a diameter of the top hemisphere lens.
19 . The micro LED structure according to claim 5 , wherein the array of micro LEDs respectively forms an array of sidewalls at a bottom surface of the bottom epitaxial layer, and wherein the micro LED structure further comprises a reflective layer covering the array of sidewalls.
20 . The micro LED structure according to claim 19 , further comprising an insulating layer formed between the array of sidewalls and the reflective layer.
21 . The micro LED structure according to claim 20 , further comprising an array of bottom contacts formed at a bottom surface of the bottom epitaxial layer, wherein each of the bottom contacts is surrounded by the insulating layer and electrically connected with the bottom conductive structure.
22 . The micro LED structure according to claim 21 , wherein the array of bottom contacts forms an ohmic contact with the bottom conductive structure.
23 . The micro LED structure according to claim 1 , further comprising an array of bottom contacts formed at a bottom surface of the bottom epitaxial layer and electrically connected with a bottom conductive structure.
24 . The micro LED structure according to claim 5 , further comprising an integrated circuit (IC) back plane formed below and electrically connected to the bottom conductive structure.
25 . The micro LED structure according to claim 24 , wherein:
the bottom conductive structure comprises a first dielectric layer and a first array of contact holes formed in the first dielectric layer; and
the IC back plane comprises a second dielectric layer and a second array of contact holes formed in the second dielectric layer, the second array of contact holes respectively corresponding to the first array of contact holes.
26 . The micro LED structure according to claim 25 , wherein each contact hole in the first array has a width greater than a width of the corresponding contact hole in the second array.
27 . The micro LED structure according to claim 25 , wherein the first array of contact holes and the second array of contact holes are filled with metal.
28 . The micro LED structure according to claim 25 , wherein the IC back plane further comprises:
a chip circuit board formed below the second dielectric layer and the second array of contact holes.
29 . The micro LED structure according to claim 24 , wherein the bottom conductive structure is bonded with the IC back plane.
30 . The micro LED structure according to claim 1 , wherein the top epitaxial layer comprises a plurality of photonic crystals, each of the plurality of photonic crystals having a cylindrical shape or a conical shape.
31 . The micro LED structure according to claim 30 , wherein each of the plurality of photonic crystals has a height of 300 nm and a diameter of 266 nm, and adjacent photonic crystals are spaced by a distance of 50 nm.
32 . The micro LED structure according to claim 1 , wherein the top epitaxial layer is interconnected between adjacent micro LEDs.
33 . The micro LED structure according to claim 32 , wherein the top epitaxial layer forms a continuous bottom surface across the micro LED array.
34 . The micro LED structure according to claim 1 , wherein the light-emitting layer is interconnected between adjacent micro pixel structures.
35 . The micro LED structure according to claim 1 , wherein the bottom epitaxial layer is interconnected between adjacent micro pixel structures.
36 . The micro LED structure according to claim 35 , wherein the bottom epitaxial layer forms a continuous top surface across the micro LED array.
37 . The micro LED structure of a micro LED panel according to claim 1 , wherein the bottom epitaxial layer forms an array of inverted trapezoidal shapes or an array of bowl shapes.
38 . The micro LED structure according to claim 1 , wherein:
the first conductive type is N-type and the second conductive type is P-type; or
the first conductive type is P-type and the second conductive type is N-type.
39 . The micro LED structure according to claim 5 , wherein the top conductive layer is transparent and comprises oxide semiconductor-indium tin oxide (ITO).
40 . The micro LED structure according to claim 5 , wherein the bottom conductive structure comprises an array of cylindrical contact holes filled with metal.