Light emitting device with small size and large density
This application describes a light emitting device, an assembly of light emitting devices, a display comprising assemblies of light emitting devices, and methods of fabricating same. The light emitting device comprises a transistor, an LED that at least partially overlies the transistor, a reflector layer disposed between the LED and transistor, and conductive wires that connect electrically the transistor to the LED. The assembly comprises a plurality of light emitting devices, and the display comprises a plurality of assemblies.
1. A method for forming an assembly of light emitting devices, the method comprising:
providing a transistor substrate having a top surface and a bottom surface, the top surface comprising a plurality of conductive regions;
forming a plurality of transistors in the top surface of the transistor substrate;
providing an LED substrate;
forming a plurality of LEDs on the LED substrate, each LED of the plurality of LEDs having a surface area and wherein the plurality of LEDs comprises gallium nitride, indium gallium nitride, indium arsenide, aluminum gallium arsenide, gallium arsenide, gallium phosphide, gallium arsenide phosphide, or aluminum indium gallium phosphide;
forming at least one reflector layer, the at least one reflector layer at least partially overlying an LED of the plurality of LEDs;
bonding the plurality of transistors to the plurality of LEDs, wherein after bonding the plurality of transistors to the plurality of LEDs,
the at least one reflector layer is disposed between an LED of the plurality of LEDs and a transistor of the plurality of transistors,
each LED of the plurality of LEDs is connected electrically to a transistor of the plurality of transistors, and
each LED of the plurality of LEDs at least partially overlies a transistor of the plurality of transistors;
removing a thickness of the transistor substrate; and
forming a plurality of conductive wires, wherein each conductive wire of the plurality extends through the transistor substrate from conductive region of the plurality of conductive regions to the bottom surface of the transistor substrate.
2. The method of claim 1 , wherein the transistor substrate comprises single crystal silicon.
3. The method of claim 1 , wherein the transistor substrate comprises an etch-stop layer.
4. The method of claim 1 , further comprising forming a plurality of interconnects, each interconnect extending from an LED of the plurality of LEDs.
5. The method of claim 1 , further comprising providing a plurality of side reflectors, wherein the side reflectors are disposed between LEDs of adjacent light emitting devices of the plurality of light emitting devices and prevent light from adjacent light emitting devices from mutually interfering.
6. The method of claim 1 , wherein after the step of removing a thickness of the transistor substrate step, the transistor substrate has a thickness less than 20 microns.
7. The method of claim 1 , further comprising providing a backboard, wherein the backboard comprises a plurality of metal interconnects.
8. The method of claim 7 , further comprising bonding each conductive wire of the plurality of conductive wires to one of the plurality of metal interconnects.
9. The method of claim 8 , further comprising removing the LED substrate.
10. The method of claim 9 , further comprising providing a plurality of wavelength-converting layers, wherein each wavelength-converting layer at least partially overlies an LED of the plurality of LEDs.
11. The method of claim 1 , wherein the surface area of at least one LED of the plurality of LEDs is 40,000 square microns or less.
12. The method of claim 1 , wherein the surface area of at least one LED of the plurality of LEDs is 1,000 square microns or less.
13. The method of claim 1 , wherein the surface area of at least one LED of the plurality of LEDs is 100 square microns or less.