Wavelength converters, including polarization-enhanced carrier capture converters, for solid state lighting devices, and associated systems and methods
View Patent ↗Wavelength converters, including polarization-enhanced carrier capture converters, for solid state lighting devices, and associated systems and methods are disclosed. A solid state radiative semiconductor structure in accordance with a particular embodiment includes a first region having a first value of a material characteristic and being positioned to receive radiation at a first wavelength. The structure can further include a second region positioned adjacent to the first region to emit radiation at a second wavelength different than the first wavelength. The second region has a second value of the material characteristic that is different than the first value, with the first and second values of the characteristic forming a potential gradient to drive electrons, holes, or both electrons and holes in the radiative structure from the first region to the second region. In a further particular embodiment, the material characteristic includes material polarization.
1. A solid state lighting (SSL) device, comprising:
a light emitting diode configured to emit light at a first wavelength; and
a solid state radiative semiconductor structure having a first region coupled to the light emitting diode, and a second region adjacent to the first region, wherein—
the first region is positioned to absorb the light at the first wavelength and thereby generate electrons, holes, or both electrons and holes in the first region, the first region having a first material polarization, and
the second region has a second material polarization different than the first material polarization, wherein the first and second material polarizations are non-zero and form a potential gradient having an orientation at an interface between the first and second regions selected to drive the generated electrons, holes, or both electrons and holes in the radiative structure from the first region to the second region such that they radiatively recombine at the second region to emit light at a second wavelength different than the first wavelength.
2. The SSL device of claim 1 wherein the first region is an alloy of gallium nitride, and the second region is an alloy of gallium nitride different than the alloy of the first region.
3. The SSL device of claim 2 wherein the second region includes gallium indium nitride.
4. The SSL device of claim 2 wherein the first region includes gallium indium nitride with a first concentration of indium that is greater than zero, and the second region includes gallium indium nitride with a second concentration of indium greater than the first concentration.
5. The SSL device of claim 1 wherein a composition of the radiative structure has a step change at the interface.
6. The SSL device of claim 1 wherein the first and second regions are polar regions, and wherein the interface is at a c-plane of at least one of the first and second regions.
7. The SSL device of claim 1 wherein the first region includes a barrier and the second region includes a quantum well, and wherein the SSL device includes a stack of alternating barriers and quantum wells, with individual barriers comprising indium gallium nitride with a first concentration of indium, and with individual quantum well comprising indium gallium nitride with a second concentration of indium greater than the first.
8. The SSL device of claim 7 wherein the quantum wells and the barriers have the same wurtzite crystal orientation.
9. The SSL device of claim 1 wherein the light emitting diode includes an active region positioned adjacent to an N-type material and a P-type material, the active region being positioned to emit the light at the first wavelength directed to the radiative structure.
10. The SSL device of claim 1 wherein the first and second regions include a material having a common constituent, wherein the constituent has a first concentration in the first material and a second concentration different than the first concentration in the second material.
11. A method for forming a solid state lighting device, comprising:
selecting a radiative structure having a first region and a second region, the first region having a first non-zero value of a material characteristic, the second region having a second non-zero value of the material characteristic, with the first and second values producing a potential gradient to drive at least one of electrons and holes in the radiative structure from the first region to the second region; and
positioning the radiative structure with the first region proximate to a radiation source to absorb radiation at a first wavelength, and with the second region positioned to receive energy from the first region and emit the energy at a second wavelength via radiative recombination, wherein the second wavelength is different than the first wavelength,
wherein the material characteristic includes material polarization, and wherein selecting a radiative structure includes selecting a radiative structure with the first region having a first material polarization value and the second region having a second material polarization value different than the first material polarization value, with the differences between the first and second material polarization values forming an electric field at an interface between the first and second regions.
12. The method of claim 11 wherein the radiation source include a light emitting diode.
13. The method of claim 11 , further comprising disposing the first and second materials adjacent to and fixed relative to each other.
14. The method of claim 11 wherein selecting the first material includes selecting the first material to include gallium nitride, and wherein selecting the second material includes selecting the second material to include gallium indium nitride.
15. The method of claim 11 wherein selecting the first material includes selecting the first material to include gallium indium nitride with a first concentration of indium, and wherein selecting the second material includes selecting the second material to include gallium indium nitride with a second concentration of indium different than the first concentration.
16. The method of claim 11 , further comprising selecting both the first and second materials to have wurtzite crystal structures.
17. The method of claim 11 , further comprising selecting both the first and second materials to have the same crystal orientation.