Light emitting diode devices with bonding and/or ohmic contact-reflective material
A metal stack of layers contacting an N-type layer of a light emitting diode (LED) device comprises: an ohmic contact layer electrically contacting the N-type layer and having a work function value that is less than or equal to a work function value of the N-type layer; a reflective layer electrically contacting the ohmic contact layer; a first material barrier layer electrically contacting the reflective layer; a current carrying layer electrically contacting the first material barrier layer; and a second material barrier layer electrically contacting the current carrying layer. LED devices incorporate the metal stack of layer as a bonding material and/or as an ohmic contact-reflective material. Methods of making and using the metal stacks and LED devices are also provided.
1. A light emitting diode (LED) device comprising:
a plurality of mesas, each of the mesas comprising semiconductor layers, the semiconductor layers including an N-type layer, an active region, and a P-type layer, and each mesa having a top surface and at least one mesa sidewall;
a plurality of trenches between the mesas defined by respective mesa sidewalls and each having a bottom surface, each of the trenches containing an N-ohmic contact-reflective material electrically contacting the N-type layer of each of the mesas, the N-ohmic contact-reflective material being multi-layered, and comprising:
an ohmic contact layer electrically contacting the N-type layer and having a work function value that is less than or equal to a work function value of the N-type layer,
a reflective layer electrically contacting the ohmic contact layer,
a first material barrier layer electrically contacting the reflective layer,
a current carrying layer electrically contacting the first material barrier layer, and
a second material barrier layer electrically contacting the current carrying layer;
an N-electrode metal contained by the N-ohmic contact-reflective material,
a dielectric material which insulates the P-type layer and the active region from the N-ohmic contact-reflective material; and
a P-electrode metal in electrical contact with the P-type layer of each of the mesas.
2. The LED device of claim 1 , wherein the N-ohmic contact-reflective material is in direct contact with the N-type layer.
3. The LED device of claim 1 , wherein the N-type layer comprises n-GaN and:
the ohmic contact layer comprises: aluminum (Al), titanium (Ti), or aluminum-doped zinc oxide (AZO),
the reflective layer comprises silver (Ag) or gold (Au);
the first and second material barrier layers each independently comprise: titanium (Ti), chromium (Cr), platinum (Pt), cobalt (Co), palladium (Pd), or tungsten (W), and
the current carrying layer comprises: copper (Cu), gold (Au), or aluminum (Al).
4. The LED device of claim 1 , wherein:
the ohmic contact layer comprises a thickness in a range of greater than or equal to 5 Å to less than or equal to 200 Å,
the reflective layer comprises a thickness of greater than or equal to 1000 Å,
the first and second material barrier layers each independently comprise a thickness of greater than or equal to 1000 Å, and
the current carrying layer comprises a thickness of greater than or equal to 5000 Å.
5. The LED device of claim 1 , wherein the N-ohmic contact-reflective material further comprises a first material migration suppression layer electrically contacting the reflective layer and the first material barrier layer; and a second material migration suppression layer electrically contacting the current carrying layer and the second material barrier layer.
6. The LED device of claim 5 , wherein the first and second material migration suppression layers each independently comprise nickel (Ni) or palladium (Pd), and/or independently comprise a thickness in a range of greater than or equal to 50 Å to less than or equal to 1000 Å.
7. The LED device of claim 1 further comprising a P-ohmic contact-reflective material containing the P-electrode metal, wherein the P-ohmic contact-reflective material has the same structure as the N-ohmic contact-reflective material.
8. The LED device of claim 1 , wherein each of the mesas has at least one characteristic dimension of less than 100 micrometers, the character dimension being selected from the group consisting of: height, width, and depth.
9. The LED device of claim 1 , wherein the semiconductor layers are epitaxial semiconductor layers having an overall thickness in a range of from 2 μm to 10 μm.
10. The LED device of claim 1 , wherein each of the mesas includes sidewalls of the semiconductor layers defining 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.
11. The LED device of claim 1 , wherein the plurality of mesas are integral to a monolithic die.
12. The LED device of claim 1 , wherein the semiconductor layers are on a substrate.
13. A method of manufacturing a light emitting diode (LED) device comprising:
preparing a plurality of mesas and trenches, each of the mesas comprising semiconductor layers, the semiconductor layers including an N-type layer, an active region, and a P-type layer, and each mesa having a top surface and at least one mesa sidewall, and the trenches defined by respective mesa sidewalls and each having a bottom surface;
exposing the N-type layer;
preparing an N-ohmic contact-reflective material electrically contacting the N-type layer of each of the mesas by:
depositing an ohmic contact layer electrically contacting the N-type layer and having a work function value that is less than or equal to a work function value of the N-type layer,
depositing a reflective layer electrically contacting the ohmic contact layer,
depositing a first material barrier layer electrically contacting the reflective layer,
depositing a current carrying layer electrically contacting the first material barrier layer, and
depositing a second material barrier layer electrically contacting the current carrying layer;
depositing and patterning an N-electrode metal contained by the N-ohmic contact-reflective material and a P-electrode metal in electrical contact with the P-type layer of each of the mesas; and
depositing and patterning a dielectric material which insulates the P-type layer and the active region from the N-ohmic contact-reflective material.
14. The method of claim 13 comprising depositing the N-ohmic contact-reflective material directly on the N-type layer.
15. The method of claim 13 , wherein the N-type layer comprises n-GaN, and the ohmic contact layer comprises: aluminum (Al), titanium (Ti), or aluminum-doped zinc oxide (AZO); the reflective layer comprises silver (Ag) or gold (Au); the first and second material barrier layers each independently comprise: titanium (Ti), chromium (Cr), platinum (Pt), cobalt (Co), palladium (Pd), or tungsten (W); and the current carrying layer comprises: copper (Cu), gold (Au), or aluminum (Al).
16. The method of claim 13 , wherein:
the ohmic contact layer comprises a thickness in a range of greater than or equal to 5 Å to less than or equal to 200 Å,
the reflective layer comprises a thickness of greater than or equal to 1000 Å,
the first and second material barrier layers each independently comprise a thickness of greater than or equal to 1000 Å, and
the current carrying layer comprises a thickness of greater than or equal to 5000 Å.
17. The method of claim 13 further comprising: depositing a first material migration suppression layer electrically contacting the reflective layer and the first material barrier layer; and/or a second material migration suppression layer electrically contacting the current carrying layer and the second material barrier layer.
18. The method of claim 17 , wherein the first and second material migration suppression layers each independently comprise nickel (Ni) or palladium (Pd), and/or independently comprise a thickness in a range of greater than or equal to 50 Å to less than or equal to 1000 Å.
19. The method of claim 13 , wherein a P-bonding material is also prepared contacting the P-type layer by depositing the ohmic contact layer electrically contacting the P-type layer, depositing the reflective layer electrically contacting the ohmic contact layer, depositing the first N-bonding material barrier layer electrically contacting the reflective layer, depositing the current carrying layer electrically contacting the first material barrier layer.
20. The method of claim 13 , wherein each of the mesas has at least one characteristic dimension of less than 100 micrometers, the character dimension being selected from the group consisting of: height, width, and depth.