Micrometer scale light emitting diode displays on patterned templates and substrates
Techniques, devices, and systems are disclosed and include LEDs with a first flat region, at a first height, including a plurality of epitaxial layers such as a first n-layer, a first p-layer, and a first active layer. A second flat region at a second height and parallel to the first flat region includes at least a second n-layer. Sloped sidewalls connect the first flat region and the second flat region and include at least a third n-layer. The p-layer of the first flat region is thicker that at least a portion of the third region. A p-contact is formed on the first p-layer and an n-contact is formed on the second n-layer.
1. A micro-light emitting diode (uLED) comprising a plurality of epitaxial layers including an n-layer, an active layer, and a p-layer, the plurality of epitaxial layers forming a structure comprising:
a first flat region, at a first height from an LED base, comprising a first portion of the n-layer, a first portion of the active layer, and a first portion of the p-layer;
a second flat region, at a second height from the LED base and parallel to the first flat region, comprising a second portion of the n-layer;
a sloped sidewall connecting the first flat region and the second flat region and comprising at least a third portion of the n-layer, a second portion of the active layer, and a second portion of the p-layer, the first portion of the p-layer of the first flat region being thicker than the second portion of the p-layer of the sloped sidewall;
a p-contact formed on the first portion of the p-layer; and
an n-contact formed on the second portion of the n-layer.
2. The uLED of claim 1 , wherein the sloped sidewalls at least partially surround the first flat region and the second flat region at least partially surrounds the sloped sidewalls.
3. The uLED of claim 2 , further comprising a pocket such that the first flat region is a base of the pocket and the sloped sidewalls are the sides of the pocket.
4. The uLED of claim 3 , further comprising a light converting phosphor in the pocket.
5. The uLED of claim 4 , further comprising at least one of a silicone encapsulant and an epoxy encapsulant on the second portion of the n-layer and the light converting phosphor.
6. The uLED of claim 1 , wherein the first flat region is a prism having a lateral extent between 2 micrometers and 100 micrometers and a thickness between 1 micrometers and 50 micrometers.
7. The uLED of claim 1 , wherein a difference between the first height and the second height is between 1 micrometers and 10 micrometers.
8. The uLED of claim 1 , wherein an angle created by the first flat region and the sloped sidewalls is between 45 degrees and 160 degrees.
9. The uLED of claim 1 , wherein the second portion of the p-layer has a thickness of less than 80% of a thickness of the first portion of the p-layer of the first flat region.
10. The uLED of claim 9 , wherein the thickness of the second portion of the p-layer confines greater than 90% of a forward bias hole injection to the first flat region.
11. The uLED of claim 9 , wherein the epitaxial layers of the first flat region comprise a first crystallographic plane orientation and the epitaxial layers is of the sloped sidewall comprises a second crystallographic plane orientation.
12. The uLED of claim 1 , wherein the plurality of epitaxial layers further comprise a junction n-layer, a junction-active layer, a junction p-layer and tunnel junction disposed above the first p-layer such that the tunnel junction layer faces the first p-layer.
13. An array of micro-light emitting diodes (uLEDs), comprising:
a patterned substrate having mesas with top surfaces and sloped sidewalls extending from the top surfaces toward a non-patterned surface of the patterned substrate;
a continuous epitaxial layer on the patterned substrate, the continuous epitaxial layer comprising an n-layer adjacent the patterned substrate, a p-layer, and an active layer positioned between the n-layer and the p-layer, the continuous epitaxial layer having a first portion, a second portion and a third portion, the first portion positioned adjacent to the top surfaces of the mesas, the second portion positioned adjacent the non-patterned surface, and a third portion positioned adjacent the sloped sidewalls, the third portion having a thickness less than a thickness of at least one of the first portion and the second portion;
p-contacts electrically coupled to the first portion of the epitaxial layer;
n-contacts electrically coupled to the second portion of the epitaxial layer and extending vertically from the second portion of the epitaxial layer toward a plane extending laterally from the top surfaces of the mesas; and
an insulating material positioned between the third portion of the continuous epitaxial layer and the n-contact.
14. The array of uLEDs of claim 13 , wherein the mesas have a hexagon shape.
15. The array of uLEDs of claim 13 , wherein the third portion of the epitaxial layer adjacent to the sloped sidewalls has a thickness less than 80% of a thickness of the first portion of the epitaxial layer adjacent to the top surfaces of the mesas.
16. An array of micro-light emitting diodes (uLEDs), comprising:
a backplane;
a plurality of uLEDs, wherein each uLED comprises:
an n-contact and a p-contact electrically coupled to the backplane;
a pocket defined by a base layer and a top layer connected via a sloped sidewall layer extending from the base layer outwardly and away from the backplane, the base layer, the top layer and the sloped sidewall layer comprising a light emitting active region, the sloped sidewall layer being thinner than at least one of the base layer and the top layer;
the n-contact extending vertically from the backplane towards a plane extending laterally from the top layer of the pockets, the n-contact surrounding the base layer and the top layer and providing optical isolation between adjacent uLEDs of the plurality of uLEDs;
the p-contact electrically coupled to the base layer; and
an insulating material attached to the pocket and positioned between the n-contacts and the p-contacts.
17. The array of uLEDs of claim 16 , wherein each uLED further comprises a phosphor material, the phosphor material filling the pockets.
18. The array of uLEDs of claim 17 , wherein a first plurality of uLEDs comprises a first phosphor material having first spectral properties, and a second plurality of uLEDs comprises a second phosphor material having second spectral properties.
19. The array of uLEDs of claim 18 , wherein each uLED further comprises an optical elements above the phosphor material.
20. The array of uLEDs of claim 17 , wherein the sloped sidewall has a current injection into the light emitting active region of less than 10% of a current injection into the light emitting active region of either the top layer or the base layer.
21. The device of claim 1 , wherein the uLED has a width of less than 100 micrometers.
22. The device of claim 13 , wherein the uLED has a width of less than 100 micrometers.
23. The device of claim 16 , wherein the uLED has a width of less than 100 micrometers.