Light emitting device with LED stack for display and display apparatus having the same
A light emitting device for a display includes a substrate and first, second, and third LED sub-units, a first transparent electrode between the first and second LED sub-units and in ohmic contact with the first LED sub-unit, a second transparent electrode between the second and third LED sub-units and in ohmic contact with the second LED sub-unit, a third transparent electrode between the second transparent electrode and the third LED sub-unit and in ohmic contact with the third LED sub-unit, at least one current spreader connected to at least one of the first, second, and third LED sub-units, electrode pads disposed on the substrate, and through-hole vias formed through the substrate, in which at least one of the through-hole vias is formed through the substrate and the first and second LED sub-units.
1. A light emitting device for a display, comprising:
a first substrate;
a first LED sub-unit disposed under the first substrate;
a second LED sub-unit disposed under the first LED sub-unit;
a third LED sub-unit disposed under the second LED sub-unit;
a first transparent electrode interposed between the first and second LED sub-units, and in ohmic contact with a lower surface of the first LED sub-unit;
a second transparent electrode interposed between the second and third LED sub-units, and in ohmic contact with a lower surface of the second LED sub-unit;
a third transparent electrode interposed between the second transparent electrode and the third LED sub-unit, and in ohmic contact with an upper surface of the third LED sub-unit;
at least one current spreader connected to at least one of the first, second, and third LED sub-units;
electrode pads disposed on the first substrate; and
through-hole vias formed through the first substrate to electrically connect the electrode pads to the first, second, and third LED sub-units,
wherein at least one of the through-hole vias is formed through the first substrate, the first LED sub-unit, and the second LED sub-unit.
2. The light emitting device of claim 1 , wherein the first, second, and third LED sub-units comprise first, second, and third LED stacks configured to emit red light, green light and blue light, respectively.
3. The light emitting device of claim 1 , further comprising a distributed Bragg reflector interposed between the first substrate and the first LED sub-unit.
4. The light emitting device of claim 1 , wherein the first substrate comprises GaAs.
5. The light emitting device of claim 4 , further comprising a second substrate disposed under the third LED sub-unit.
6. The light emitting device of claim 5 , wherein the second substrate is a sapphire substrate or a GaN substrate.
7. The light emitting device of claim 5 , wherein:
the first LED sub-unit, the second LED sub-unit, and the third LED sub-unit are independently drivable;
light generated from the first LED sub-unit is configured to be emitted to the outside of the light emitting device through the second LED sub-unit, the third LED sub-unit, and the second substrate; and
light generated from the second LED sub-unit is configured to be emitted to the outside of the light emitting device through the third LED sub-unit and the second substrate.
8. The light emitting device of claim 1 , wherein the electrode pads comprise:
a common electrode pad commonly electrically connected to the first, second, and third LED sub-units; and
a first electrode pad, a second electrode pad, and a third electrode pad electrically connected to the first LED sub-unit, the second LED sub-unit, and the third LED sub-unit, respectively.
9. The light emitting device of claim 8 , wherein the common electrode pad is electrically connected to a plurality of through-hole vias.
10. The light emitting device of claim 8 , wherein:
the second electrode pad is electrically connected to the second LED sub-unit through a first through-hole via formed through the first substrate and the first LED sub-unit; and
the third electrode pad is electrically connected to the third LED sub-unit through a second through-hole via formed through the first substrate, the first LED sub-unit, and the second LED sub-unit.
11. The light emitting device of claim 10 , wherein the first electrode pad is electrically connected to the first substrate.
12. The light emitting device of claim 10 , wherein the first electrode pad is electrically connected to the first LED sub-unit through a third through-hole via formed through the first substrate.
13. The light emitting device of claim 11 , wherein:
the at least one current spreader comprises:
a first current spreader connected to the first LED sub-unit;
a second current spreader connected to the second LED sub-unit; and
a third current spreader connected to the third LED sub-unit; and
the first, second, and third current spreaders are separated from the first, second, and third transparent electrodes, respectively.
14. The light emitting device of claim 1 , wherein one of the electrode pads disposed on the first substrate is electrically connected to the first, second, and third transparent electrodes through a plurality of through-hole vias.
15. The light emitting device of claim 1 , wherein one of the electrode pads disposed on the first substrate is connected to the first substrate.
16. The light emitting device of claim 1 , further comprising:
a first color filter disposed between the third transparent electrode and the second transparent electrode; and
a second color filter disposed between the second LED sub-unit and the first transparent electrode.
17. The light emitting device of claim 16 , wherein the first color filter and the second color filter comprise insulation layers having different refractive indices.
18. The light emitting device of claim 1 , further comprising an insulation layer disposed between the first substrate and the electrode pads, and covering side surfaces of the first, second, and third LED sub-units.
19. The light emitting device of claim 1 , wherein the at least one current spreader has a body at least partially surrounding one of the through-hole via, and a projection extending outwardly from the body.
20. The light emitting device of claim 19 , wherein the body has a substantially annular shape and the projection has a width less than the diameter of the body.
21. A display apparatus comprising:
a circuit board; and
a plurality of light emitting devices arranged on the circuit board, at least one of the light emitting devices comprises:
a first substrate;
a first LED sub-unit disposed under the first substrate;
a second LED sub-unit disposed under the first LED sub-unit;
a third LED sub-unit disposed under the second LED sub-unit;
a first transparent electrode interposed between the first and second LED sub-units, and in ohmic contact with a lower surface of the first LED sub-unit;
a second transparent electrode interposed between the second and third LED sub-units, and in ohmic contact with a lower surface of the second LED sub-unit;
a third transparent electrode interposed between the second transparent electrode and the third LED sub-unit, and in ohmic contact with an upper surface of the third LED sub-unit;
at least one current spreader connected to at least one of the first, second, and third LED sub-units;
electrode pads disposed on the first substrate; and
through-hole vias formed through the first substrate to electrically connect the electrode pads to the first, second, and third LED sub-units,
wherein:
at least one of the through-hole vias is formed through the first substrate, the first LED sub-unit, and the second LED sub-unit; and
the electrode pads of the light emitting device are electrically connected to the circuit board.
22. The display apparatus of claim 21 , wherein each of the light emitting devices further comprises a second substrate coupled to the third LED sub-unit.