Light emitting diode devices with current spreading layer

1. A light emitting diode (LED) device comprising:

a plurality of mesas defining pixels, each of the mesas comprising semiconductor layers, the semiconductor layers including an N-type layer, an active region, and a P-type layer, each of the mesas having a height less than or equal to their width;

an N-contact material in a space between each of the mesas, the N-contact material providing optical isolation between each of the mesas, and electrically contacting the N-type layer of each of the mesas along sidewalls of the N-type layers;

a dielectric material which insulates sidewalls of the P-type layer and the active region from the N-contact material;

a current spreading layer on the P-type layer, the current spreading layer having a first portion and a second portion;

a hard mask layer above the second portion of the current spreading layer, the hard mask layer comprising sidewalls defining a hard mask opening;

a liner layer conformally-deposited in the hard mask opening above the first portion of the current spreading layer and on the sidewalls of the hard mask layer;

a P-metal material plug on the liner layer;

a passivation layer on the hard mask layer and the N-contact material; and

an under bump metallization layer on the passivation layer and in contact with the P-metal material plug, a portion of the passivation layer located between the under bump metallization layer and the hard mask layer.

2. The LED device of claim 1 , further comprising a dielectric layer on the second portion of the current spreading layer below the hard mask layer; a via opening defined by sidewalls of the dielectric layer and the first portion of the current spreading layer; and a P-contact layer below the hard mask layer and the P-metal material plug, the P-contact layer located in the via opening on the first portion of the current spreading layer, the sidewalls of the dielectric layer, and on at least a portion of the dielectric layer.

3. The LED device of claim 2 , wherein the P-contact layer comprises a reflective metal, and the current spreading layer comprises a transparent material.

4. The LED device of claim 1 , wherein the plurality of mesas comprises an array of mesas.

5. The LED device of claim 1 , wherein the current spreading layer comprises a transparent conductive oxide (TCO).

6. The LED device of claim 5 , wherein the current spreading layer comprises indium tin oxide (ITO) or indium zinc oxide (IZO).

7. The LED device of claim 2 , wherein the P-contact layer comprises one or more of nickel (Ni) and silver (Ag), and the dielectric layer comprises silicon dioxide (SiO 2 ).

8. The LED device of claim 2 , further comprising a guard layer covering the P-contact layer.

9. The LED device of claim 8 , wherein the guard layer comprises one or more of titanium-platinum (TiPt), titanium-tungsten (TiW), and titanium-tungsten nitride (TiWN).

10. The LED device of claim 1 , wherein the semiconductor layers have a thickness in a range of from 2 μm to 10 μm.

11. The LED device of claim 1 , wherein the dielectric material is in a form of outer spacers comprising a material selected from the group consisting of SiO 2 , AlO x , and SiN, having a thickness in a range of from 200 nm to 1 μm.

12. The LED device of claim 1 , wherein the space between each of the mesas comprises a trench having a depth from a top surface of each of the mesas in a range of from 0.5 inn to 2 μm.

13. The LED device of claim 1 , wherein each of the mesas includes sidewalls of the semiconductor layers, each having a first segment and a second segment, wherein the first segments of the sidewalls define an angle in a range of from 60 degrees to 90 degrees from a horizontal plane that is parallel with the N-type layer and the P-type layer; and the second segments of the sidewalls form an angle with a top surface of a substrate upon which the mesas are formed in a range of from 75 to less than 90 degrees.