ETCH REMOVAL OF CURRENT DISTRIBUTION LAYER FOR LED CURRENT CONFINEMENT

• US 20150187740A1
• Filed: 12/27/2013
• Published: 07/02/2015
• Est. Priority Date: 12/27/2013
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: LuxVue Techonology Corporation (Apple Inc.)
• Inventors: McGroddy, Kelly, Hu, Hsin-Hua, Bibl, Andreas, Chan, Clayton Ka Tsun
• Granted Patent: US 9,583,466 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: G09G 3/32 semiconductive, e.g. using light-emitting diodes [LED]
• 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 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 2924/0002 Not covered by any one of groups H01L24/00, H01L24/00 and H01L2224/00
• 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 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 33/14 with a carrier transport control structure, e.g. highly-doped semiconductor layer or current-blocking structure
• CPC Class Codes: H01L 33/20 with a particular shape, e.g. curved or truncated substrate

Abstract

A method and structure for forming an array of LED devices is disclosed. The LED devices in accordance with embodiments of the invention may include a confined current injection area in which a current spreading layer protrudes away from a cladding layer in a pillar configuration so that the cladding layer is wider than the current spreading layer pillar.

Claims

1. An LED device comprising:

an active layer between a first current spreading layer pillar and a second current spreading layer, wherein the first current spreading layer pillar 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 pillar and the active layer; and

a second cladding layer between the second current spreading layer and the active layer;

wherein the first current spreading layer pillar protrudes away from the first cladding layer and the first cladding layer is wider than the first current spreading layer pillar.

2. The LED device of claim 1, further comprising a passivation layer spanning along a surface of the first cladding layer and sidewalls of the first current spreading layer pillar.

3. The LED device of claim 2, further comprising an opening in the passivation layer on a surface of the first current spreading layer pillar opposite the first cladding layer.

4. The LED device of claim 3, further comprising a conductive contact within the opening in the passivation layer and in electrical contact with the first current spreading layer pillar.

5. The LED device of claim 4, wherein the conductive contact is not in direct electrical contact with the first cladding layer.

6. The LED device of claim 1, wherein the second current spreading layer is wider than the first current spreading layer pillar.

7. The LED device of claim 1, wherein the LED device is supported by a post, and a surface area of a top surface of the post is less than the surface area of a bottom surface of the first current spreading layer pillar.

8. The LED device of claim 1, wherein the LED device is incorporated within a display area of a portable electronic device.

9. The LED device of claim 1, wherein the first current spreading layer pillar is doped with a p-dopant.

10. The LED device of claim 9, wherein the first current spreading layer comprises GaP and the first cladding layer comprise a material selected from the group consisting of AlInP, AlGaInP, and AlGaAs.

11. The LED device of claim 1, wherein the active layer of the LED device has a maximum width of 100 μ

m or less, and the first current spreading layer pillar has a maximum width of 10 μ

m or less.

12. The LED device of claim 1, wherein the active layer of the LED device has a maximum width of 20 μ

m or less, and the first current spreading layer pillar has a maximum width of 10 μ

m or less.

13. The LED device of claim 1, wherein the active layer includes 1-3 quantum well layers.

14. The LED device of claim 1, wherein the LED device is bonded to a display substrate within a display area of the display substrate, and the LED device is in electrical connection with working circuitry in the display substrate.

15. The LED device of claim 1, wherein the LED device is bonded to a display substrate within a display area of the display substrate, and the LED device is in electrical connection with a micro chip bonded to the display substrate within the display area.

16. A method of forming an LED device array comprising:

patterning a p-n diode layer of an LED substrate to form an array of current spreading layer pillars separated by an array of confinement trenches in a current spreading layer of the p-n diode layer, wherein the confinement trenches extend through the current spreading layer and expose a cladding layer of the p-n diode layer underneath the current spreading layer;

forming a sacrificial release layer over the array of current spreading layer pillars and the cladding layer;

bonding the LED substrate to a carrier substrate;

removing a handle substrate from the LED substrate.

patterning the p-n diode layer laterally between the array of current spreading layer pillars to form an array of LED devices, wherein each LED device includes a current spreading layer pillar of the array of current spreading layer pillars.

17. The method of claim 16, wherein patterning the p-n diode layer comprises etching through a top current spreading layer, a top cladding layer, one or more quantum well layers, and the cladding layer to expose the sacrificial release layer.

18. The method of claim 16, further comprising forming an array of bottom electrically conductive contacts on and in electrical contact with the array of current spreading layer pillars prior to forming the sacrificial release layer over the array of current spreading layer pillars and the cladding layer.

19. The method of claim 16, further comprising patterning the sacrificial release layer to form an array of openings in the sacrificial release layer over the array of current spreading layer pillars prior to bonding the LED substrate to the carrier substrate.

20. The method of claim 19, further comprising bonding the LED substrate to the carrier substrate with a bonding material such that the bonding material is located within the array of openings in the sacrificial release layer.

21. The method of claim 16, further comprising removing the sacrificial release layer.

22. The method of claim 21, further comprising transferring a portion of the array of LED devices from the carrier substrate to the receiving substrate.

23. The method of claim 22, further comprising transferring a portion of the array of LED devices from the carrier substrate to the receiving substrate with an electrostatic transfer head assembly.

24. A method of operating a display comprising:

sending a control signal to a driving transistor; and

driving a current through an LED device including a confined current injection area in response to the control signal;

wherein the LED device includes a current spreading layer pillar that protrudes away from a cladding layer, and the cladding layer is wider than the current spreading layer pillar.

25. The method of claim 24, wherein the current is from 1 nA-400 nA.

26. The method of claim 25, wherein the current is from 1 nA-30 nA.

27. The method of claim 26, wherein a current density flowing through the LED device is from 0.001 A/cm² to 3 A/cm².

28. The method of claim 25, wherein the current is from 200 nA-400 nA.

29. The method of claim 28, wherein a current density flowing through the LED device is from 0.2 A/cm² to 4 A/cm².

30. The method of claim 25, wherein the current is from 100 nA-300 nA

31. The method of claim 30, wherein a current density flowing through the LED device is from 0.01 A/cm²-30 A/cm².

32. The method of claim 24, wherein the display is a portable electronic device.