Abstract
Refractive-index (RI)-matched nanostructures are implemented in GaN-based light-emitting diodes (LEDs) for enhancing light output efficiency. The RI-matched indium tin oxide (ITO) nanostructures are successfully implemented in GaN-based lateral LEDs by using ITO sol–gel and nanoimprint lithography. The ITO sol–gel nanostructures annealed at 300 °C have RI of 1.95, showing high transparency of 90% and high diffused transmittance of 34%. Consequently, the light output power in LEDs with the RI-matched nanostructures increases by 8% in comparison with that in LEDs containing flat ITO. Ray tracing and finite-difference time-domain (FDTD) simulations show that the RI-matched nanostructures on the transparent current spreading layer dramatically reduce Fresnel reflection loss at the interface of the current spreading layer with the nanostructure and extract confined waveguide lights in LEDs.
Highlights
Group III-nitride light-emitting diodes (LEDs) are promising candidates for next-generation lighting sources because of their high efficiency, long life, and environmental friendliness.[1,2,3] To replace conventional light sources with LEDs, the quantum efficiency of LEDs should be further increased
An internal quantum efficiency (IQE) value of nearly 80% has been reported,[4,5] but there is still much room for enhancement of light extraction efficiency (LEE). This is due to the fact that most of the generated photons from the active layer are captured by LEDs because of total internal re ection (TIR) at the interface of semiconductor with air.[6,7]
We report a way to implement novel hexagonal pyramid-shaped nanostructures using an RI-matched indium tin oxide (ITO) sol– gel on the transparent current spreading ITO layer
Summary
Group III-nitride light-emitting diodes (LEDs) are promising candidates for next-generation lighting sources because of their high efficiency, long life, and environmental friendliness.[1,2,3] To replace conventional light sources with LEDs, the quantum efficiency of LEDs should be further increased. The RI-matched indium tin oxide (ITO) nanostructures are successfully implemented in GaN-based lateral LEDs by using ITO sol–gel and nanoimprint lithography. Implementing the RI-matched nanostructures onto LEDs improves light output power in comparison with those with at ITO.
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