Systems and Methods for Coaxial Multi-Color LED
A micro multi-color LED device includes two or more LED structures for emitting a range of colors. The two or more LED structures are vertically stacked to combine light from the two more LED structures. In some embodiments, each LED structure is connected to a pixel driver and a shared electrode. The LED structures are bonded together through bonding layers. In some embodiments, reflection layers are implemented in the device to improve the LED emission efficiency. A display panel comprising an array of the micro tri-color LED devices has a high resolution and a high illumination brightness.
1 . A single pixel multi-color micro light-emitting diode (LED) device for a display panel, comprising:
a substrate supporting a pixel driver;
a first LED epitaxial layer stacked on top of the substrate; and
a second LED epitaxial layer stacked on top of the first LED epitaxial layer,
wherein:
the first LED epitaxial layer and the second LED epitaxial layer substantially overlap laterally with one another to form a light path that combines light emitted from the first LED epitaxial layer and the second LED epitaxial layer; and
an insulation layer covers a top and a side wall of the single pixel multi-color LED device.
2 . The single pixel multi-color LED device according to claim 1 , wherein:
the second LED epitaxial layer is a top LED epitaxial layer; and
the second LED epitaxial layer forms a green light LED.
3 . The single pixel multi-color LED device according to claim 1 , further comprising a third LED epitaxial layer stacked on top of the second LED epitaxial layer, wherein the first LED epitaxial layer, the second LED epitaxial layer, and the third LED epitaxial layer substantially overlap laterally with one another to form a light path that combines light emitted from the first LED epitaxial layer, the second LED epitaxial layer, and the third LED epitaxial layer.
4 . The single pixel multi-color LED device according to claim 3 , wherein:
the third LED epitaxial layer is a top LED epitaxial layer; and
the third LED epitaxial layer forms a green light LED.
5 . The single pixel multi-color LED device according to claim 3 , wherein:
the first LED epitaxial layer forms a red light LED;
the second LED epitaxial layer forms a blue light LED; and
the third LED epitaxial layer forms a green light LED.
6 . The single pixel multi-color LED device according to claim 3 , further comprising:
a first bonding layer between the substrate and the first LED epitaxial layer;
a second bonding layer between the first LED epitaxial layer and the second LED epitaxial layer; and
a third bonding layer between the second LED epitaxial layer and the third LED epitaxial layer.
7 . The single pixel multi-color LED device according to claim 6 , wherein the second bonding layer and third bonding layer are transparent.
8 . The single pixel multi-color LED device according to claim 3 , wherein:
a bottom portion of each of the first LED epitaxial layer, the second LED epitaxial layer, and the third LED epitaxial layer is electrically connected to the pixel driver through a first-type electrode;
an upper portion of the first LED epitaxial layer is electrically connected to a first second-type electrode;
an upper portion of the second LED epitaxial layer is electrically connected to a second second-type electrode; and
an upper portion of the first LED epitaxial layer is electrically connected to a third second-type electrode.
9 . The single pixel multi-color LED device according to claim 8 , wherein:
the first-type electrode is a P-electrode and each of the first second-type electrode, the second second-type electrode, and the third second-type electrode is a N-electrode; or
the first-type electrode is a N-electrode and each of the first second-type electrode, the second second-type electrode, and the third second-type electrode is a P-electrode.
10 . The single pixel multi-color LED device according to claim 8 , wherein:
the insulation layer comprises a first opening on the bottom portion of the first LED epitaxial layer, a second opening on the bottom portion of the second LED epitaxial layer, and a third opening on the bottom portion of the third LED epitaxial layer; and
the first-type electrode is formed in the first opening, the second opening, and the third opening to contact each of the first LED epitaxial layer, the second LED epitaxial layer, and the third LED epitaxial layer, respectively.
11 . The single pixel multi-color LED device according to claim 10 , wherein:
the insulation layer further comprises a fourth opening on the upper portion of the first LED epitaxial layer, a fifth opening on the upper portion of the second LED epitaxial layer, and a sixth opening on the upper portion of the third LED epitaxial layer;
the first second-type electrode is formed in the fourth opening to contact the upper portion of the first LED epitaxial layer;
the second second-type electrode is formed in the fifth opening to contact the upper portion of the second LED epitaxial layer; and
the third second-type electrode is formed in the sixth opening to contact the upper portion of the third LED epitaxial layer.
12 . The single pixel multi-color LED device according to claim 3 , further comprising:
a first reflection layer between the substrate and the first LED epitaxial layer;
a second reflection layer between the first LED epitaxial layer and the second LED epitaxial layer; and
a third reflection layer between the second LED epitaxial layer and the third LED epitaxial layer.
13 . The single pixel multi-color LED device according to claim 12 , wherein at least one of the first reflection layer, the second reflection layer, and the third reflection layer comprises a distributed Bragg reflector (DBR) structure.
14 . The single pixel multi-color LED device according to claim 12 , wherein:
light emitted from the first LED epitaxial layer propagates through the second reflection layer and the third reflection layer; and
light emitted from the second LED epitaxial layer propagates through the third reflection layer.
15 . The single pixel multi-color LED device according to claim 3 , further comprising:
a first lower conductive layer and a first upper conductive layer formed at a bottom and a top of the first LED epitaxial layer, respectively;
a second lower conductive layer and a second upper conductive layer formed at a bottom and a top of the second LED epitaxial layer, respectively; and
a third lower conductive layer and a third upper conductive layer formed at a bottom and a top of the third LED epitaxial layer, respectively.
16 . The single pixel multi-color LED device according to claim 15 , wherein:
each of the first lower conductive layer, the second lower conductive layer, and the third lower conductive layer is electrically connected to the pixel driver through a first-type electrode;
the first upper conductive layer is electrically connected to a first second-type electrode;
the second upper conductive layer is electrically connected to a second second-type electrode; and
the third upper conductive layer is electrically connected to a third second-type electrode.
17 . The single pixel multi-color LED device according to claim 16 , wherein:
the insulation layer comprises a first opening on the first lower conductive layer, a second opening on the second lower conductive layer, and a third opening on the third lower conductive layer; and
the first-type electrode is formed in the first opening, the second opening, and the third opening to contact each of first lower conductive layer, the second lower conductive layer, and the third lower conductive layer, respectively.
18 . The single pixel multi-color LED device according to claim 17 , wherein:
the insulation layer further comprises a fourth opening on the first upper conductive layer, a fifth opening on the second upper conductive layer, and a sixth opening on the third upper conductive layer;
the first second-type electrode is formed in the fourth opening to contact the first upper conductive layer;
the second second-type electrode is formed in the fifth opening to contact the second upper conductive layer; and
the third second-type electrode is formed in the sixth opening to contact the third upper conductive layer.
19 . A micro light-emitting diode (LED) display chip, comprising:
a substrate; and
an array of single pixel multi-color micro LED devices,
wherein:
each single pixel multi-color micro LED device of the array of single pixel multi-color micro LED devices comprises a first LED epitaxial layer stacked on top of the substrate, a second LED epitaxial layer stacked on top of the first LED epitaxial layer, and a third LED epitaxial layer stacked on top of the second LED epitaxial layer;
an insulation layer covers a top and a side wall of each single pixel multi-color LED device; and
within each single pixel multi-color micro LED device, the first LED epitaxial layer, the second LED epitaxial layer, and the third LED epitaxial layer substantially overlap laterally with one another to form a light path that combines light emitted from the first LED epitaxial layer, the second LED epitaxial layer, and the third LED epitaxial layer.
20 . The micro LED display chip according to claim 19 , wherein:
the first LED epitaxial layer forms a red light LED;
the second LED epitaxial layer forms a blue light LED; and
the third LED epitaxial layer forms a green light LED.