Solid state transducer dies having reflective features over contacts and associated systems and methods
Systems and methods for improved light emitting efficiency of a solid state transducer (SST), for example light emitting diodes (LED), are disclosed. One embodiment of an SST die in accordance with the technology includes a reflective material disposed over electrical connectors on a front side of the die. The reflective material has a higher reflectivity than a base material of the connectors such that light traveling toward the connectors reflects back out of the device.
1. A light emitting diode (LED), comprising:
a transduction structure including a back side, a front side opposite the back side, a first semiconductor material having a first surface at the back side, a second semiconductor material having a second surface at the front side, and an active material between the first and second semiconductor materials;
a first electrical connector electrically coupled to the first semiconductor material, wherein the first semiconductor material extends continuously over the first surface of the first electrical connector; and
a second electrical connector electrically coupled to the transduction structure and covering a portion of the second surface of the second semiconductor material, wherein the second electrical connector includes—
a base material electrically coupled to the second semiconductor material, wherein the base material has a top surface, side surfaces and a first reflectivity, and wherein the second surface of the second semiconductor material is only partially covered by the base material, and
a reflective material completely encasing the top surface and side surfaces of the base material, wherein the reflective material has a second reflectivity higher than the first reflectivity.
2. The LED of claim 1 wherein the second electrical connector further comprises a current spreading material between the base material and the reflective material.
3. The LED of claim 2 wherein the current spreading material is directly over and covers an outer surface of the base material.
4. The LED of claim 1 wherein the base material includes a first outer surface facing the transduction structure, a second outer surface opposite the first outer surface, and third and fourth outer surfaces extending between the first and second outer surfaces, wherein the reflective material surrounds the entire second outer surface, third outer surface, and fourth outer surface.
5. The LED of claim 1 wherein the base material is a Ti—Al alloy, the current spreading material is Au, and the reflective material is at least one of Al, Ag or an Ag alloy.
6. The LED of claim 1 , further comprising a converter material at least partially surrounding the transduction structure and the second electrical connector.
7. The LED of claim 6 wherein the transduction structure is configured to emit light at a first frequency, and wherein the emitted light stimulates the converter material to emit light at a second frequency different than the first frequency.
8. The LED of claim 6 , further comprising a lens surrounding the converter material.
9. The LED of claim 1 wherein the second electrical connector comprises a plurality of traces of the base material on a surface of the second semiconductor material.
10. A method of manufacturing light emitting diode (LED) dies, the method comprising:
forming a transduction structure having a back side, a front side opposite the back side, a first semiconductor material having a first surface at the back side, a second semiconductor material having a second surface at the front side, and an active material between the first and second semiconductor materials;
forming a first electrical connector electrically coupled to the first semiconductor material such that the first semiconductor material extends continuously over the first electrical connector; and
forming a second electrical connector electrically coupled to the second semiconductor material by—
electrically coupling a base material of the second electrical connector to the second semiconductor material, wherein the base material has a top surface, side surfaces, and a first reflectivity, and wherein the second surface of the second semiconductor material is only partially covered by the base material, and
disposing a reflective material over the complete top surface and along the side surfaces of the base material, wherein the reflective material includes a second reflectivity higher than the first reflectivity.
11. The method of claim 10 , further comprising forming a current spreading material on the base material before disposing the reflective material such that the current spreading material is between the base material and the reflective material.
12. The method of claim 10 wherein the base material is a Ti—Al alloy, the current spreading material is Au, and the reflective material is at least one of Al, Ag or an Ag alloy.
13. The method of claim 10 , wherein forming the current spreading material includes forming the current spreading material such that the current spreading material directly covers an outer surface of the base material.
14. The method of claim 10 wherein the base material includes a first outer surface facing the transduction structure, a second outer surface opposite the first outer surface, and third and fourth outer surfaces extending between the first and second outer surfaces, wherein disposing the reflective material includes disposing the reflective material such that the reflective material surrounds the entire second outer surface, third outer surface, and fourth outer surface.
15. The method of claim 10 wherein forming the second electrical connector comprises disposing a plurality of traces of the base material on a surface of the second semiconductor material.
16. The method of claim 10 , further comprising providing a converter material at least partially around the transduction structure.
17. The method of claim 16 , further comprising providing a lens at least partially around the converter material.
18. The LED of claim 2 the current spreading material has a third reflectivity, and wherein the second reflectivity of the reflective material is higher than the third reflectivity.
19. The LED of claim 1 wherein the first electrical connector is at the back side of the transduction structure, and wherein the second electrical connector is buried in the transduction structure under the front side of the transduction structure.
20. The method of claim 11 wherein the current spreading material has a third reflectivity, and wherein the second reflectivity of the reflective material is higher than the third reflectivity.
21. The method of claim 10 wherein the first electrical connector is at the back side of the transduction structure, and wherein the second electrical connector is buried in the transduction structure under the front side of the transduction structure.