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LED utilizing internal color conversion with light extraction enhancements

專利號
US10868213B2
公開日期
2020-12-15
申請人
Lumileds LLC（US CA San Jose）
發(fā)明人
Robert David Armitage; Isaac Harshman Wildeson; Parijat Pramil Deb
IPC分類
H01L33/10; H01L33/00; H01L33/50; H01L33/46; H01L33/08
技術(shù)領(lǐng)域
qw,epitaxial,layer,el,pl,may,qws,dichroic,reflector,be
地域： CA CA San Jose

摘要

A light emitting diode (LED) device may include an n-type layer formed on a transparent substrate. A photoluminescent (PL) in the n-type layer quantum well (QW) and an electroluminescent (EL) QW may be formed on the n-type layer. The PL QW and the EL QW may be separated from one another by a portion of the n-type layer. A p-type layer may be formed on the EL QW. Trenches may be formed extending into the n-type layer, the trenches defining an emitting area. A passivation material may be formed on sidewalls of the trenches and n-type contacts may be formed therein. A p-type contact may be formed on an upper surface of the p-type layer. A dichroic mirror may be formed on at least a lower surface of the transparent substrate.

說明書

BACKGROUND

Semiconductor light-emitting devices including light emitting diodes (LEDs), resonant cavity light emitting diodes (RCLEDs), vertical cavity laser diodes (VCSELs), and edge emitting lasers are among the most efficient light sources currently available. Materials systems currently of interest in the manufacture of high-brightness light emitting devices capable of operation across the visible spectrum include Group III-V semiconductors, particularly binary, ternary, and quaternary alloys of gallium, aluminum, indium, and nitrogen, also referred to as III-nitride materials.

Typically, III-nitride light emitting devices are fabricated by epitaxially growing a stack of semiconductor layers of different compositions and dopant concentrations on a sapphire, silicon carbide, III-nitride, or other suitable substrate by metal-organic chemical vapor deposition (MOCVD), molecular beam epitaxy (MBE), or other epitaxial techniques. The stack often includes one or more n-type layers doped with, for example, silicon, formed over the substrate, one or more light emitting layers in an active region (e.g., a p-n diode) formed over the n-type layer or layers, and one or more p-type layers doped with, for example, magnesium, formed over the active region. Electrical contacts are formed on the n-type and p-type regions.

One class of blue and green LEDs use GaInN/GaN strained quantum wells or GaInN/GaInN strained quantum wells located between the n-type and p-type layers to generate light by the recombination of holes and electrons injected from these layers. The present disclosure generally relates to improve the efficiency of these quantum well devices.

SUMMARY

權(quán)利要求

1
What is claimed is:1. A light emitting diode (LED) device comprising:a transparent substrate;an n-type layer disposed on or above the transparent substrate;an electroluminescent (EL) quantum well (QW) formed on the n-type layer and configured to emit a first light;a photoluminescent (PL) QW formed in the n-type layer and configured to absorb at least a portion of the first light and in response emit a second light having a longer wavelength than the first light, the EL QW and the PL QW separated from one another by a portion of the n-type layer;a p-type layer formed on the EL QW; anda dichroic reflector having a greater reflectivity for the first light than for the second light, the dichroic reflector arranged to transmit the second light out of the LED device and to reflect back to the PL QW a portion of the first light transmitted through the PL QW and incident on the dichroic reflector.2. The LED device of claim 1, wherein the PL QW comprises multiple QWs emitting a same wavelength of light.3. The LED device of claim 1, wherein the EL QW comprises multiple QWs emitting a same wavelength of light.4. The LED device of claim 1, wherein the PL QW is adjacent to a depletion region of a p-n junction between the n-type layer and the p-type layer.5. The LED device of claim 1, wherein the thickness of the p-type layer is optimized to exploit self-interference of the EL QW.6. The LED device of claim 1, wherein the EL QW and the p-type electrode are separated by a distance equivalent to approximately 0.25 to approximately 0.45 times a peak wavelength of an emission of the EL QW in the p-type layer.7. The LED device of claim 1, wherein the dichroic reflector is disposed on a surface of the transparent substrate opposite from the n-type layer.8. The LED device of claim 7, wherein the dichroic reflector extends along one or more sidewalls of the transparent substrate, n-type layer, EL QW, and p-type layer.9. The LED device of claim 7, wherein the dichroic reflector comprises a stack of dielectric layers having different refractive indices.10. The LED device of claim 1, wherein the dichroic reflector has a thickness of approximately one quarter of a peak wavelength of light emitted by the EL QW.11. The LED device of claim 1, wherein EL QW is located within a depletion region of a p-n junction between the n-type layer and the p-type layer.12. The LED device of claim 7, further comprisingtrenches formed through at least an entire thickness of the p-type layer and an entire thickness of the EL QW to expose the n-type layer, the trenches defining an emitting area;a passivation material formed on sidewalls of the trenches and an upper surface of the p-type layer;n-type contacts formed in the trenches; anda p-type contact formed on the upper surface of the p-type layer in the emitting area.13. The LED device of claim 1, wherein the dichroic reflector is disposed between the transparent substrate and the n-type layer.14. The LED device of claim 13, wherein the dichroic reflector comprises multiple layers of Group III-V semiconductor materials having different compositions.15. The LED device of claim 14, wherein one or more of the multiple layers of Group III-V semiconductor materials are oxidized such that they have a lower refractive index than as-grown material.16. The LED device of claim 14, wherein one or more of the multiple layers of Group III-V semiconductor materials comprise dopants of one or more of Si and Ge and are processed to include voids such that they have a lower refractive index than as-grown material.17. The LED device of claim 14, further comprising:a first epitaxial layer formed on the substrate between the substrate and the dichroic reflector; anda second epitaxial layer formed between the dichroic reflector and the n-type layer.18. The LED device of claim 1 wherein the PL QW is configured to emit green light.19. The LED device of claim 1 comprising a second PL QW formed in the n-type layer and configured to absorb at least a portion of the first light and in response emit a third light having a longer wavelength than the first light, the PL QW and the second PL QW separated from one another by a portion of the n-type layer.20. The LED device of claim 19 wherein the second PL QW is configured to emit red light.21. The LED device of claim 20 wherein the PL QW is configured to emit green light.
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