Investigation of InGaN-Based Green Micro-Photonic-Crystal- Light-Emitting-Diodes with Bottom, Nanoporous, Distributed Bragg Reflectors

Abstract

In this work, an InGaN-based, green micro-photonic crystal-light-emitting-diode (µ-PCLED), which incorporates a nanoporous, GaN-distributed Bragg reflector (DBR) to form a Fabry–Perot (FP) cavity, was fabricated and characterized. Simulations for the µ-PCLED’s optical features were systematically performed and analyzed. Numerical results revealed that the p-GaN photonic crystal (PC) with a filling factor of 0.3 is beneficial for improving the coupling constants of the first- and second-order Bragg diffractions. In addition, based on the product of quantum well (QW) and PC confinement factors, four to six pairs of InGaN QWs should be the preferable design. In order to achieve single-wavelength emission and small full-width at half-maximum (FWHM), the thickness of the n-GaN layer was controlled to be thinner than 920 nm, leading to more than 20 nm wavelength separation between two adjacent FP modes. Experimentally, the fabricated InGaN-based µ-PCLED with a mesa diameter of 30 µm can emit 545 nm green light with FWHM of about 10 nm and negligible blue-shift of about 3 nm in spontaneous emission under the injection current of 1 to 10 mA. Our simulation and experimental results demonstrate that the p-GaN PC design can effectively resolve the wavelength instability issue.

The micro-LED roadmap: status quo and prospects

“…Using blue-light absorption filler including black matrix has also been reported [154] to improve the color purity. Pixelated arrays also require photonic control in collimation, polarization, and possibly focusing of each pixel; photonic engineering involving micro-lens [136], DBR [155] and metasurfaces [134,135] will need to be applied based on specific use cases.…”

Design of photonic crystals for light‐emitting diodes

“…Hong et al. designed and studied an InGaN‐based green micro‐photonic crystal light‐emitting diode (μ‐PC LED) combining a 2D nanopore PC structure with a DBR, which successfully achieved green light generation and solved the problem of wavelength instability 93 . Figure 23C shows a schematic representation of the structure.…”

“…Hong et al designed and studied an InGaN-based green micro-photonic crystal light-emitting diode (μ-PC LED) combining a 2D nanopore PC structure with a DBR, which successfully achieved green light generation and solved the problem of wavelength instability. 93 shows a schematic representation of the structure. In Figure 23D, it can be seen that at an injection current of 1-10 mA, a 30 m diameter InGaN-based PC LED would emit green light at 545 nm with an full width at half maximum of about 10 nm and a negligible blueshift of about 3 nm in spontaneous emission, and the green PC LED was expected to be called the next-generation light source.…”

“…Right: 30 μm green μ‐PC LED current‐dependent peak wavelength and full width at half maximum (FWHM). Reproduced from refs 92, 93. with permission of Springer and MDPI.…”