MICRO LIGHT-EMITTING DIODE (LED) STRUCTURE
An exemplary micro light-emitting diode (LED) structure includes an array of micro LEDs. Each micro LED in the array includes: a bottom epitaxial layer of a first conductive type; a light-emitting layer, formed on the bottom epitaxial layer; a top epitaxial layer of a second conductive type, formed on the light-emitting layer; and a top contact layer, formed on the top epitaxial layer and having a continuous closed shape.
1 . A microlight-emitting diode (LED) structure, comprising:
an array of micro LEDs, wherein each micro LED in the array comprises:
a bottom epitaxial layer of a first conductive type;
a light-emitting layer, formed on the bottom epitaxial layer;
a top epitaxial layer of a second conductive type, formed on the light-emitting layer; and
a top contact layer, formed on the top epitaxial layer and having a continuous closed shape.
2 . The micro LED structure according to claim 1 , wherein the continuous closed shape comprises: a circular shape, an annular shape, or an annular-square shape with an annular inner portion and a square peripheral portion.
3 . The micro LED structure according to claim 1 , wherein the top contact layer is continuously formed on the top epitaxial layer in the array of micro LEDs.
4 . The micro LED structure according to claim 1 , wherein the top contact layer is formed at an edge of the respective micro LED and around a center axis of the respective micro LED.
5 . The micro LED structure according to claim 1 , wherein the top contact layer comprises a conductive material.
6 . The micro LED structure according to claim 5 , wherein the conductive material of the top contact layer is metal.
7 . The micro LED structure according to claim 1 , wherein each micro LED in the array further comprises a top conductive layer formed on the top epitaxial layer and the top contact layer.
8 . The micro LED structure according to claim 7 , wherein the top conductive layer is transparent and comprises indium tin oxide (ITO).
9 . The micro LED structure according to claim 1 , wherein the top epitaxial layer comprises a first trench between adjacent micro LEDs.
10 . The micro LED structure according to claim 9 , wherein the top contact layer is formed at an edge of the first trench.
11 . The micro LED structure according to claim 9 , wherein the bottom epitaxial layer comprises a second trench formed at a position corresponding to the first trench.
12 . The micro LED structure according to claim 1 , wherein each micro LED in the array further comprises a micro lens formed above the top epitaxial layer.
13 . The micro LED structure according to claim 12 , wherein a gap is formed between the micro lens and an adjacent micro lens.
14 . The micro LED structure according to claim 12 , wherein the micro lens comprises a top hemisphere lens and a bottom spacer below the top hemisphere lens.
15 . The micro LED structure according to claim 14 , wherein a width of the bottom spacer is greater than a diameter of the top hemisphere lens.
16 . The micro LED structure according to claim 14 , wherein a height of the bottom spacer is determined based on a diameter of the top hemisphere lens.
17 . The micro LED structure according to claim 1 , wherein:
the bottom epitaxial layer comprises a second trench between adjacent micro LEDs; and
each micro LED in the array further comprises a reflective layer formed on a sidewall of the second trench.
18 . The micro LED structure according to claim 17 , wherein each micro LED in the array further comprises an insulating layer formed between the second trench and the reflective layer.
19 . The micro LED structure according to claim 18 , wherein each micro LED in the array further comprises:
a bottom contact pad formed at a bottom surface of the bottom epitaxial layer; and
a bottom conductive structure formed below the bottom contact and the bottom epitaxial layer;
wherein the bottom contact pad is surrounded by the insulating layer and electrically connected to the bottom conductive structure.
20 . The micro LED structure according to claim 1 , wherein each micro LED in the array further comprises:
a bottom conductive structure below the bottom epitaxial layer; and
an integrated circuit (IC) back plane formed below and electrically connected to the bottom conductive structure.
21 . The micro LED structure according to claim 20 , wherein:
the bottom conductive structure comprises a first dielectric layer and a first contact hole formed in the first dielectric layer; and
the IC back plane comprises a second dielectric layer and a second contact hole formed in the second dielectric layer, the second contact hole corresponding to the first contact hole.
22 . The micro LED structure according to claim 21 , wherein a width of the first contact hole is greater than a width of the second contact hole.
23 . The micro LED structure according to claim 21 , wherein a first metal is filled in the first contact hole and a second metal is filled in the second contact hole.
24 . The micro LED structure according to claim 23 , the first metal in the first contact hole is bonded to the second metal in the second contact hole.
25 . The micro LED structure according to claim 21 , wherein the IC back plane further comprises:
a chip circuit board formed below the second dielectric layer and the second contact hole.
26 . The micro LED structure according to claim 1 , wherein the top epitaxial layer comprises a plurality of photonic crystals.
27 . The micro LED structure according to claim 26 , wherein each of the plurality of photonic crystals has a cylindrical shape or a conical shape.
28 . The micro LED structure according to claim 26 , 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.
29 . The micro LED structure according to claim 1 , wherein the top epitaxial layer is interconnected between adjacent micro LEDs.
30 . The micro LED structure according to claim 29 , wherein the top epitaxial layer forms a continuous bottom surface across the array of micro LEDs.
31 . The micro LED structure according to claim 1 , wherein the light-emitting layer is interconnected between adjacent micro LEDs.
32 . The micro LED structure according to claim 1 , wherein the bottom epitaxial layer is interconnected between adjacent micro LEDs.
33 . The micro LED structure according to claim 32 , wherein the bottom epitaxial layer forms a continuous top surface across the array of micro LEDs.
34 . The micro LED structure according to claim 1 , wherein the bottom epitaxial layer forms an inverted trapezoidal shape or a bowl shape.
35 . 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.