LED with internally confined current injection area

• US 9,450,147 B2
• Filed: 02/28/2014
• Issued: 09/20/2016
• Est. Priority Date: 12/27/2013
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: Apple Inc.
• Inventors: McGroddy, Kelly, Hu, Hsin-Hua, Bibl, Andreas, Chan, Clayton Ka Tsun, Haeger, Daniel Arthur
• Primary Examiner(s): Dulka, John P
• Assistant Examiner(s): Peters, Charles R
• Application Number:
  US14/194,509
• Publication Number:
  US 20150187991A1
• Time in Patent Office: 935 Days
• US Class Current: 1/1
• CPC Class Codes: G09G 3/32 semiconductive, e.g. using light-emitting diodes [LED]
• CPC Class Codes: H01L 2224/75305 comprising protrusions
• CPC Class Codes: H01L 2224/75725 in the upper part of the bonding apparatus, e.g. in the bonding head
• CPC Class Codes: H01L 2224/7598 specially adapted for batch processes
• CPC Class Codes: H01L 2224/82203 Thermocompression bonding
• CPC Class Codes: H01L 24/75 Apparatus for connecting with bump connectors or layer connectors
• CPC Class Codes: H01L 24/95 at chip-level, i.e. with connecting carried out on a plurality of singulated devices, i.e. on diced chips
• CPC Class Codes: H01L 25/0753 the devices being arranged next to each other
• CPC Class Codes: H01L 27/016 Thin-film circuits
• CPC Class Codes: H01L 27/156 two-dimensional arrays
• CPC Class Codes: H01L 2924/00 Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
• CPC Class Codes: H01L 2924/12041 LED
• CPC Class Codes: H01L 2924/12042 LASER
• CPC Class Codes: H01L 2924/12044 OLED
• CPC Class Codes: H01L 2924/15153 the die mounting substrate comprising a recess for hosting the device
• CPC Class Codes: H01L 33/0016 having at least two p-n junctions
• CPC Class Codes: H01L 33/0093 Wafer bonding; Removal of the growth substrate
• CPC Class Codes: H01L 33/0095 Post-treatment of devices, e.g. annealing, recrystallisation or short-circuit elimination
• CPC Class Codes: H01L 33/06 within the light emitting region, e.g. quantum confinement structure or tunnel barrier
• CPC Class Codes: H01L 33/14 with a carrier transport control structure, e.g. highly-doped semiconductor layer or current-blocking structure
• CPC Class Codes: H01L 33/145 : with a current-blocking structure
• CPC Class Codes: H01L 33/16 : with a particular crystal structure or orientation, e.g. polycrystalline, amorphous or porous
• CPC Class Codes: H01L 33/20 : with a particular shape, e.g. curved or truncated substrate
• CPC Class Codes: H01L 33/30 : containing only elements of Group III and Group V of the Periodic Table
• CPC Class Codes: H01L 33/42 : Transparent materials

Abstract

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.

Claims

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 μ

m 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 μ

m or less.

4. The LED device of claim 1, wherein the LED device has a maximum lateral dimension of 20 μ

m 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 μ

m to 50 μ

m.

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 μ

m 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.