Light emitting diode (LED) stack for a display
A light emitting diode (LED) stack for a display includes a first LED sub-unit having a first surface and a second surface, a second LED sub-unit disposed on the first surface of the first LED sub-unit, a third LED sub-unit disposed on the second LED sub-unit, a reflective electrode disposed on the second side of the second LED sub-unit and forming ohmic contact with the first LED sub-unit, and an ohmic electrode interposed between the first LED sub-unit and the second LED sub-unit and forming ohmic contact with the first LED sub-unit, in which the second LED sub-unit and the third LED sub-unit are configured to transmit light generated from the first LED sub-unit, and the third LED sub-unit is configured to transmit light generated from the second LED sub-unit.
1. A light emitting diode (LED) stack for a display, comprising:
a first LED sub-unit having a first surface and a second surface;
a second LED sub-unit disposed on the first surface of the first LED sub-unit;
a third LED sub-unit disposed on the second LED sub-unit;
a reflective electrode disposed on the second surface of the first LED sub-unit and forming ohmic contact with the first LED sub-unit; and
an ohmic electrode interposed between the first LED sub-unit and the second LED sub-unit and forming ohmic contact with the first LED sub-unit,
wherein:
the second LED sub-unit and the third LED sub-unit are configured to transmit light generated from the first LED sub-unit; and
the third LED sub-unit is configured to transmit light generated from the second LED sub-unit.
2. The LED stack for a display of claim 1 , wherein the first, second, and third LED sub-units comprise first, second, and third LED stacks, respectively.
3. The LED stack for a display of claim 1 , wherein the LED stack comprises a micro LED having a surface area less than about 200 square μm.
4. The LED stack for a display of claim 1 , wherein the reflective electrode and the ohmic electrode have different reflective indices from each other.
5. The LED stack for a display of claim 2 , wherein the first, second, and third LED stacks are configured to emit red light, green light, and blue light, respectively.
6. The LED stack for a display of claim 2 , further comprising:
a first color filter interposed between the first LED stack and the second LED stack, and configured to transmit light generated from the first LED stack and reflect light generated from the second LED stack; and
a second color filter interposed between the second LED stack and the third LED stack, and configured to transmit light generated from the first and second LED stacks and reflect light generated from the third LED stack.
7. The LED stack for a display of claim 6 , wherein each of the first color filter and the second color filter comprises at least one of a low pass filter, a band pass filter, and a band stop filter.
8. The LED stack for a display of claim 7 , wherein each of the first and second color filters comprises a distributed Bragg reflector.
9. The LED stack for a display of claim 2 , further comprising:
a support substrate;
a first bonding layer interposed between the support substrate and the first LED stack;
a second bonding layer interposed between the first LED stack and the second LED stack; and
a third bonding layer interposed between the second LED stack and the third LED stack,
wherein:
the second bonding layer is configured to transmit light generated from the first LED stack; and
the third bonding layer is configured to transmit light generated from the first and second LED stacks.
10. The LED stack for a display of claim 9 , wherein:
the first bonding layer adjoins the reflective electrode; and
the second bonding layer adjoins the ohmic electrode.
11. The LED stack for a display of claim 10 , further comprising:
a second transparent electrode forming ohmic contact with a p-type semiconductor layer of the second LED stack; and
a third-p transparent electrode forming ohmic contact with a p-type semiconductor layer of the third LED stack.
12. The LED stack for a display of claim 11 , wherein the second bonding layer adjoins an n-type semiconductor layer of the first LED stack, and the third bonding layer adjoins an n-type semiconductor layer of the second LED stack.
13. The LED stack for a display of claim 12 , further comprising:
a first color filter interposed between the first LED stack and the second LED stack and configured to transmit light generated from the first LED stack and reflect light generated from the second LED stack; and
a second color filter interposed between the second LED stack and the third LED stack, and configured to transmit light generated from the first and second LED stacks and reflect light generated from the third LED stack,
wherein the first color filter is disposed on the second bonding layer and the second color filter is disposed on the third bonding layer.
14. A display apparatus comprising a plurality of pixels arranged on a support substrate,
wherein at least some of the pixels comprise the LED stack of claim 2 .
15. The display apparatus of claim 14 , wherein:
each of the first, second, and third LED stacks comprises a p-type semiconductor layer and an n-type semiconductor layer;
each of the p-type semiconductor layers of the first, second, and third LED stacks is electrically connected to a common line; and
each of the n-type semiconductor layers of the first, second, and third LED stacks is electrically connected to different lines from each other.
16. The display apparatus of claim 15 , wherein the common line comprises a data line and the different lines comprise scan lines.
17. The display apparatus of claim 14 , further comprising:
a lower insulation layer covering side surfaces of the first, second, and third LED stacks,
the lower insulation layer comprising openings exposing the ohmic electrode, the reflective electrode, the second LED stack, and the third LED stack.
18. The display apparatus of claim 17 , wherein the lower insulation layer comprises a distributed Bragg reflector configured to reflect red, green, and blue light.
19. The display apparatus of claim 15 , wherein the reflective electrode comprises the common line and is continuously disposed over the plurality of pixels.
20. The display apparatus of claim 14 , wherein the reflective electrode is disposed within each pixel region.