Abstract
We report theoretical and experimental analysis of antireflective subwavelength structures (SWSs) on GaP substrates to enhance the light output with a uniform light distribution of AlGaInP-based red light-emitting diodes (LEDs). Scaling issues on the optical performance are analyzed by the calculation results from finite-difference time-domain (FDTD) and rigorous coupled-wave analysis (RCWA) methods. The optical simulation reveals that SWSs with a period of 100–150 nm achieve highest optical output power, while maintaining a uniform light field distribution, in the subwavelength regime. To validate our theoretical results, disordered SWSs with a tapered shape were fabricated on a GaP layer of AlGaInP red LEDs by lithography-free dry etching of Ag nanoparticles. The SWS-integrated LED shows a uniform light output distribution with an improved light output power compared with the conventional LED.
Highlights
Today, light-emitting diodes (LEDs) offer a significant promise for efficient energy usage in lighting and display applications
We have systematically investigated the light extraction characteristics of SWSintegrated AlGaInP-based red LEDs with different periods/heights based on three-dimensional finitedifference time-domain (FDTD) and rigorous coupled-wave analysis (RCWA) methods
We performed a theoretical analysis of subwavelength structures (SWSs) on GaP substrates by RCWA, finite-difference time-domain (FDTD), and 2D grating equation for achieving a high light output power with uniform light distribution
Summary
Light-emitting diodes (LEDs) offer a significant promise for efficient energy usage in lighting and display applications. SWS-integrated LEDs showed a significant improvement in light extraction because of the introduction of a graded-index media in the semiconductor/air interface.[10,11,12,13] The combination of microstructures and SWSs were reported to maximize the light extraction efficiency by reducing both the total internal reflection (TIR) loss and Fresnel reflection loss.[2,14,15] various structures based on SWSs and graded-index media have been developed for high efficiency LEDs, there have been relatively fewer studies on the comprehensive optical modeling of SWS-integrated LEDs. diffraction energy distributions support our analysis. To validate the results of our analysis, we demonstrate a fabricated SWS-integrated red AlGaInP LED with a nanoscale pattern. We further discuss fabrication details and measurement results of the fabricated LEDs
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