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:
semiconductor layers including an N-type layer, an active region, and a P-type layer;
an N-bonding material electrically contacting the N-type layer, the N-bonding material being multi-layered and comprising:
an ohmic contact layer directly on and 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 directly on and electrically contacting the ohmic contact layer;
a first N-bonding material barrier layer electrically contacting the reflective layer;
a current carrying layer electrically contacting the first N-bonding material barrier layer; and
a second N-bonding material barrier layer electrically contacting the current carrying layer;
a P-bonding material electrically contacting the P-type layer and being isolated from the N-bonding material; and
a first dielectric material which insulates the P-type layer and the active region from the N-bonding material.
2 . The LED device of claim 1 , wherein a thickness of the ohmic contact layer is less than or equal to 20% of a thickness of the reflective layer.
3 . The LED device of claim 1 , wherein:
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 N-bonding 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 3 , wherein the N-type layer comprises n-GaN.
5 . 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 N-bonding 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.
6 . The LED device of claim 1 , wherein the N-bonding material further comprises a first N-bonding material migration suppression layer electrically contacting the reflective layer and the first material barrier layer; and a second N-bonding material migration suppression layer electrically contacting the current carrying layer and the second material barrier layer.
7 . The LED device of claim 6 , wherein the first and second N-bonding 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.
8 . The LED device of claim 1 , wherein the P-bonding material is the same as the N-bonding material.
9 . The LED device of claim 1 , wherein the semiconductor layers are on a substrate and the N-bonding material directly contacts the N-type layer, and the device further comprises an N-pad electrically contacting the N-bonding layer and a P-pad electrically contacting the P-bonding layer, and a second dielectric material which insulates the N-bonding material from the P-bonding material.
10 . The LED device of claim 9 , which is in a form of a chip scale package.
11 . The LED device of claim 1 , which is in a form of a monolithic array, wherein a first portion of the N-type layer forms a monolithic body, and a second portion of the N-type layer in combination with the active region and the P-type layer form a plurality of mesas integral to the monolithic body, the N-bonding material directly contacts the first portion of the N-type layer, and 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.
12 . A method of manufacturing a light emitting diode (LED) device comprising:
preparing a plurality of semiconductor layers including an N-type layer, an active region, and a P-type layer;
exposing the N-type layer;
preparing an N-bonding material contacting the N-type layer by:
depositing an ohmic contact layer directly on and 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 directly on and electrically contacting the ohmic contact layer;
depositing a first N-bonding material barrier layer electrically contacting the reflective layer;
depositing a current carrying layer electrically contacting the first material barrier layer; and
depositing a second N-bonding material barrier layer electrically contacting the current carrying layer; and
depositing a dielectric material which insulates the P-type layer and the active region from the N-bonding material.
13 . The method of claim 12 , wherein the N-type layer comprises n-GaN, and the ohmic contact layer comprises: aluminum (AI), 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).
14 . The method of claim 12 , 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.
15 . The method of claim 12 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.
16 . The method of claim 15 , 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.
17 . The method of claim 12 , 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.
18 . The method of claim 12 , wherein a first portion of the N-type layer forms a monolithic body, and a second portion of the N-type layer in combination with the active region and the P-type layer form a plurality of mesas integral to the monolithic body, the N-bonding material directly contacts the first portion of the N-type layer, and 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.