Solid state lighting devices with improved contacts and associated methods of manufacturing
Solid state lighting (“SSL”) devices with improved contacts and associated methods of manufacturing are disclosed herein. In one embodiment, an SSL device includes an SSL structure having a first semiconductor material, a second semiconductor material spaced apart from the first semiconductor material, and an active region between the first and second semiconductor materials. The SSL device also includes a first contact on the first semiconductor material and a second contact on the second semiconductor material, where the first and second contacts define the current flow path through the SSL structure. The first or second contact is configured to provide a current density profile in the SSL structure based on a target current density profile.
1. A solid state lighting (“SSL”) device, comprising:
an SSL structure having a first semiconductor material, a second semiconductor material spaced apart from the first semiconductor material, and an active region between the first and second semiconductor materials;
a first contact on the first semiconductor material; and
a second contact on the second semiconductor material, the second contact including a conductive material encapsulating a plurality of pads of a contact material, the plurality of pads of the contact material being sized to spatially modulate a current density of the SSL structure, the plurality of pads of the contact material each having an inner conductive portion with an inner portion contact resistance and an outer conductive portion surrounding the inner conductive portion, the outer conductive portion having an outer portion contact resistance greater than the inner portion contact resistance,
wherein the plurality of pads of the contact material form an interface with the second semiconductor material having a first contact resistance, and wherein the conductive material has a second contact resistance higher than the first contact resistance.
2. The SSL device of claim 1 wherein the plurality of pads of the contact material extend partially from the second semiconductor material into the conductive material.
3. The SSL device of claim 1 wherein the plurality of pads of the contact material extend completely from the second semiconductor material to a conductive surface of the conductive material.
4. The SSL device of claim 1 wherein the plurality of pads of the contact material individually have a shape different than others in different regions of the SSL structure.
5. The SSL device of claim 1 wherein the plurality of pads of the contact material individually have a geometric profile different than others in different regions of the SSL structure.
6. The SSL device of claim 1 wherein the conductive material includes at least one of tin oxide (ITO), aluminum zinc oxide (AZO), or fluorine-doped tin oxide (FTO).
7. The SSL device of claim 1 wherein:
the second contact is laterally spaced apart from the first contact;
the first semiconductor material includes a P-type gallium nitride (“GaN”) material;
the second semiconductor material includes an N-type GaN material; and
the active region includes at least one of a bulk indium gallium nitride (“InGaN”) material, an InGaN single quantum well (“SQW”), and GaN/InGaN multiple quantum wells (“MQWs”).
8. The SSL device of claim 1 wherein:
the second contact is opposite the first contact; and
the second contact includes a contact finger on the second semiconductor material.
9. The SSL device of claim 1 wherein the current density of the SSL structure is determined at least partially based on a target current density profile in the SSL structure.
10. A method of forming a solid state lighting (“SSL”) device, comprising:
forming an SSL structure on a substrate material, the SSL structure having a first semiconductor material, a second semiconductor material spaced apart from the first semiconductor material, and an active region between the first and second semiconductor materials;
forming a first contact on the first semiconductor material; and
forming a second contact on the second semiconductor material, the second contact including a conductive material encapsulating a plurality of pads of a contact material, the plurality of pads of the contact material being sized to spatially modulate a current density of the SSL structure, the plurality of pads of the contact material each having an inner conductive portion with an inner portion contact resistance and an outer conductive portion surrounding the inner conductive portion, the outer conductive portion having an outer portion contact resistance greater than the inner portion contact resistance,
wherein the plurality of pads of the contact material form an interface with the second semiconductor material having a first contact resistance, and wherein the conductive material has a second contact resistance higher than the first contact resistance.
11. The method of claim 10 wherein the plurality of pads of the contact material extend partially from the second semiconductor material into the conductive material.
12. The method of claim 10 wherein the plurality of pads of the contact material extend completely from the second semiconductor material to a conductive surface of the conductive material.
13. The method of claim 10 further comprising determining the current density of the SSL structure at least partially based on a target current density profile in the SSL structure.
14. A solid state lighting (“SSL”) device, comprising:
an SSL structure having a first semiconductor material, a second semiconductor material spaced apart from the first semiconductor material, and an active region between the first and second semiconductor materials;
a first contact on the first semiconductor material; and
a second contact on the second semiconductor material, the second contact including a conductive material encapsulating a plurality of pads of a contact material, the plurality of pads of the contact material being shaped to spatially modulate a current density of the SSL structure, the plurality of pads of the contact material each having an inner conductive portion with an inner portion contact resistance and an outer conductive portion surrounding the inner conductive portion, the outer conductive portion having an outer portion contact resistance greater than the inner portion contact resistance,
wherein the plurality of pads of the contact material form an interface with the second semiconductor material having a first contact resistance, and wherein the conductive material has a second contact resistance higher than the first contact resistance.
15. The SSL device of claim 14 wherein the conductive material includes at least one of tin oxide (ITO), aluminum zinc oxide (AZO), or fluorine-doped tin oxide (FTO).
16. The SSL device of claim 14 wherein the plurality of pads of the contact material individually have a size different than others in different regions of the SSL structure.
17. The SSL device of claim 1 , wherein the plurality of pads include a first pad having a first lateral dimension and a second pad having a second lateral dimension, and wherein a first lateral distance between the first pad and the first contact is smaller than a second distance between the second pad and the first contact, and wherein the first lateral dimension is greater than the second lateral dimension.
18. The SSL device of claim 1 , wherein the contact material includes at least one of copper (Cu), aluminum (Al), silver (Ag), gold (Au), or platinum (Pt).
19. The method of claim 10 , wherein the plurality of pads include a first pad having a first lateral dimension and a second pad having a second lateral dimension, and wherein a first lateral distance between the first pad and the first contact is smaller than a second distance between the second pad and the first contact, and wherein the first lateral dimension is greater than the second lateral dimension.
20. The method of claim 10 , wherein the contact material includes at least one of copper (Cu), aluminum (Al), silver (Ag), gold (Au), or platinum (Pt).
21. The SSL device of claim 14 , wherein the plurality of pads include a first pad having a first lateral dimension and a second pad having a second lateral dimension, and wherein a first lateral distance between the first pad and the first contact is smaller than a second distance between the second pad and the first contact, and wherein the first lateral dimension is greater than the second lateral dimension.
22. The SSL device of claim 14 , wherein the contact material includes at least one of copper (Cu), aluminum (Al), silver (Ag), gold (Au), or platinum (Pt).