LED with internally confined current injection area
Methods and structures for forming arrays of LED devices are disclosed. The LED devices in accordance with embodiments of the invention may include an internally confined current injection area to reduce non-radiative recombination due to edge effects. Several manners for confining current may include etch removal of a current distribution layer, etch removal of a current distribution layer and active layer followed by mesa re-growth, isolation by ion implant or diffusion, quantum well intermixing, and oxide isolation.
1. An LED device comprising:
an active layer between a first current spreading layer and a second current spreading layer, wherein the first current spreading layer is doped with a first dopant type and the second current spreading layer is doped with a second dopant type opposite the first dopant type;
a first cladding layer between the first current spreading layer and the active layer;
a second cladding layer between the second current spreading layer and the active layer;
a current confinement region laterally surrounding a current injection region to confine current that flows through the active layer to an interior portion of the LED device and away from sidewalls of the LED device; and
a bottom conductive contact directly on and in ohmic contact with the current injection region:
wherein the LED device has a maximum lateral dimension of 50 μm or less, and the bottom conductive contact is bonded to a bottom electrode of a subpixel within a display area of a display substrate.
2. The LED device of claim 1 , wherein the LED device does not include a distributed Bragg reflector layer on opposite sides of the active layer.
3. The LED device of claim 1 , wherein the current injection region has a maximum width of 10 μm or less.
4. The LED device of claim 1 , wherein the LED device has a maximum lateral dimension of 20 μm or less.
5. The LED device of claim 1 , wherein the display substrate is incorporated within a display area of a portable electronic device.
6. The LED device of claim 1 , wherein the LED device is in electrical connection with:
a subpixel driver circuit in the display substrate, or
a micro chip bonded to the display substrate within the display area, wherein the micro chip comprises a subpixel driver circuit.
7. The LED device of claim 1 , wherein:
the current injection region comprises a pillar structure comprising the first current spreading layer, the first cladding layer, and the active layer;
the current confinement region comprises a confinement barrier fill laterally surrounding the pillar structure active layer.
8. The LED device of claim 7 , wherein the confinement barrier fill has a larger bandgap than one or more quantum well layers in the active layer.
9. The LED device of claim 7 , wherein the confinement barrier fill has a higher resistivity than the first current spreading layer, the first cladding layer, and the active layer.
10. The LED device of claim 7 , wherein the confinement barrier fill comprises a buffer layer and a barrier layer.
11. The LED device of claim 7 , wherein the confinement barrier fill comprises a p-n-p junction.
12. The LED device of claim 1 , wherein:
the current injection region is located within the first current spreading layer; and
the current confinement region comprises a modified confinement barrier region within the first current spreading layer and laterally surrounds the current injection region.
13. The LED device of claim 12 , wherein the modified confinement barrier region is characterized by a higher resistivity than the current injection region.
14. The LED device of claim 12 , wherein the modified confinement barrier region is doped with the second dopant type.
15. The LED device of claim 12 , wherein the first dopant type is P-type and the second dopant type is N-type.
16. An LED device comprising:
an active layer between a first current spreading layer and a second current spreading layer, wherein the first current spreading layer is doped with a first dopant type and the second current spreading layer is doped with a second dopant type opposite the first dopant type;
a first cladding layer between the first current spreading layer and the active layer;
a second cladding layer between the second current spreading layer and the active layer;
a current confinement region laterally surrounding a current injection region to confine current that flows through the active layer to an interior portion of the LED device and away from sidewalls of the LED device;
wherein the current injection region comprises a pillar structure comprising the first current spreading layer, the first cladding layer, and the active layer, and the current confinement region comprises a confinement barrier fill laterally surrounding the pillar structure active layer; and
a bottom conductive contact directly on and in ohmic contact with a bottom surface of the pillar structure of the current injection region, and directly on a bottom surface of the confinement barrier fill.
17. The LED device of claim 16 , wherein the bottom conductive contact is directly on and in ohmic contact with the first current spreading layer.
18. The LED device of claim 16 , wherein the bottom conductive contact comprises a material selected from the group consisting of a conductive oxide, a metal, and a metal alloy.
19. The LED device of claim 16 , wherein the LED device has a maximum lateral dimension of 1 μm to 50 μm.
20. The LED device of claim 16 wherein the bottom conductive contact is bonded to a bottom electrode of a subpixel within a display area of a display substrate.
21. The LED device of claim 16 , wherein the confinement barrier fill has a larger bandgap than one or more quantum well layers in the active layer.
22. The LED device of claim 16 , wherein the confinement barrier fill has a higher resistivity than the first current spreading layer, the first cladding layer, and the active layer.
23. The LED device of claim 16 , wherein the confinement barrier fill comprises a buffer layer and a barrier layer.
24. The LED device of claim 16 , wherein the confinement barrier fill comprises a p-n-p junction.
25. An LED device comprising:
an active layer between a first current spreading layer and a second current spreading layer, wherein the first current spreading layer is doped with a first dopant type and the second current spreading layer is doped with a second dopant type opposite the first dopant type;
a first cladding layer between the first current spreading layer and the active layer;
a second cladding layer between the second current spreading layer and the active layer;
a current confinement region laterally surrounding a current injection region to confine current that flows through the active layer to an interior portion of the LED device and away from sidewalls of the LED device; and
a bottom conductive contact directly on and in ohmic contact with the current injection region;
wherein a material transition from the pillar structure active layer to the confinement barrier fill is a continuous crystal structure without discrete sidewalls between the pillar structure active layer and the confinement barrier fill.
26. The LED device of claim 25 , wherein the LED device has a maximum lateral dimension of 50 μm or less.
27. The LED device of claim 26 , wherein the bottom conductive contact is bonded to a bottom electrode of a subpixel within a display area of a display substrate.
28. The LED device of claim 25 , wherein the confinement barrier fill has a larger bandgap than one or more quantum well layers in the active layer.
29. The LED device of claim 25 , wherein the confinement barrier fill has a higher resistivity than the first current spreading layer, the first cladding layer, and the active layer.
30. The LED device of claim 25 , wherein the confinement barrier fill comprises a buffer layer and a barrier layer.
31. The LED device of claim 25 , wherein the confinement barrier fill comprises a p-n-p junction.