Micro LED based display panel
Light emitting structures and methods of fabrication are described. In an embodiment, LED coupons are transferred to a carrier substrate and then patterned to LED mesa structures. Patterning may be performed on heterogeneous groups of LED coupons with a common mask set. The LED mesa structure are then transferred in bulk to a display substrate. In an embodiment, a light emitting structure includes an arrangement of LEDs with different thickness, and corresponding bottom contacts with different thicknesses bonded to a display substrate.
1. A light emitting structure comprising:
a light emitting diode (LED) bonded to an electrode pad of a substrate, wherein the LED comprises an inorganic semiconductor-based p-n diode, and a metallic bottom contact bonded to the electrode pad;
an insulating fill layer laterally surrounding the LED and the metallic bottom contact;
wherein a planar bottom surface of the metallic bottom contact is bonded to a planar top surface of the electrode pad with a metal-metal bond, and a planar bottom surface of the insulating fill layer is bonded to a planar top surface of the substrate with an oxide-oxide bond.
2. The light emitting structure of claim 1 , wherein the LED is mounted within a well structure embedded within the insulating fill layer.
3. The light emitting structure of claim 2 , wherein the well structure is a reflective well structure, including a reflective metal layer laterally surrounding a well material, wherein the well material is laterally surrounding the LED within the well structure.
4. The light emitting structure of claim 3 , wherein the reflective metal layer is a continuous layer that laterally surrounds and spans underneath the LED, and within an opening in the well material directly underneath the LED.
5. The light emitting structure of claim 4 , wherein:
the substrate is a complementary metal-oxide-semiconductor (CMOS) substrate.
6. The light emitting structure of claim 3 , wherein the p-n diode has a maximum width of less than 5 microns, and maximum height of less than 3 microns.
7. The light emitting structure of claim 6 , wherein the reflective well structure includes a reflective sidewall characterized by a sidewall angle of 50-80 degrees to horizontal.
8. The light emitting structure of claim 7 , further comprising a micro-optic element with sidewalls over the LED and the reflective well structure, wherein the sidewalls of the micro-optic element are characterized by a sidewall angle of 70-85 degrees to horizontal.
9. The light emitting structure of claim 7 , further comprising a micro-optic element with reflective sidewalls surrounding an optical material over the LED and the reflective well structure, wherein the optical material is filled with a color conversion material, and the reflective sidewalls of the micro-optic element are characterized by a sidewall angle of 45-60 degrees to horizontal.
10. The light emitting structure of claim 6 , further comprising:
a micro-optic element over the LED and the reflective well structure; and
a filter over the micro-optic element, wherein the micro-optic element includes an optical material filled with quantum dots, and the filter encapsulates the optical material filled with quantum dots.
11. The light emitting structure of claim 10 , wherein the filter includes a recycling portion to reflect light emitted from the LED, and a collimation portion above the recycling portion to only pass light emitted from the quantum dots that is approximately at normal incidence.
12. The light emitting structure of claim 6 , further comprising a half-ball lens over the LED and well structure.
13. A light emitting structure comprising:
a first light emitting diode (LED) comprising a first inorganic semiconductor-based p-n diode designed to emit a first color emission, and a first metallic bottom contact bonded to a first electrode pad of a substrate;
a second LED comprising a second inorganic semiconductor-based p-n diode designed to emit a second color emission different from the first color emission, and a second metallic bottom contact bonded to a second electrode pad of the substrate;
wherein the first metallic bottom contact is thicker than the second metallic bottom contact, and the second inorganic semiconductor-based p-n diode is thicker than the first inorganic semiconductor-based p-n diode; and
wherein the first and second metallic bottom contacts are embedded within an insulating fill layer, and planar bottom surfaces of the first metallic bottom contact and the second metallic bottom contact are bonded to planar top surfaces of the first electrode pad and the second electrode pad with metal-metal bonds, and a planar bottom surface of the insulating fill layer is bonded to a planar top surface of the substrate with an oxide-oxide bond.
14. The light emitting structure of claim 13 , wherein the substrate is a complementary metal-oxide-semiconductor (CMOS) substrate.
15. The light emitting structure of claim 14 , wherein the first metallic bottom contact is thicker than the second metallic bottom contact by a first thickness, and the second inorganic semiconductor-based p-n diode is thicker than the first inorganic semiconductor-based p-n diode by approximately the first thickness.
16. The light emitting structure of claim 15 , wherein top surfaces of the first and second inorganic semiconductor-based p-n diodes are co-planar.
17. The light emitting structure of claim 13 , wherein the first LED is mounted within a first well structure, and the second LED is mounted within a second well structure.
18. The light emitting structure of claim 17 , wherein the second well structure is taller than the first well structure.
19. The light emitting structure of claim 18 , wherein the first and second well structures, are embedded within the insulating fill layer.
20. The light emitting structure of claim 18 , wherein the first well structure is a first reflective well structure, and the second well structure is a second reflective well structure.
21. The light emitting structure of claim 17 , further comprising a micro-optic element with reflective sidewalls over the first LED.