Mechanisms of the Asymmetric Light Output Enhancements in $a$ -Plane GaN Light-Emitting Diodes With Photonic Crystals

Abstract

Abstract-The unique properties of nonpolar GaN lightemitting diodes (LEDs) have the advantages of generating polarized light emission. The employment of asymmetric 2-D photonic crystals (PhCs) can further enhance the light polarization ratio. In addition, it was generally recognized that the Purcell effect can increase the internal quantum efficiency of the LEDs with PhCs. In this paper, we study the properties of optical modes from different crystal planes. The Purcell effect is analyzed based on the PhCs and material crystal orientations. With different transition probability of the polarized photons in valence bands, the corresponding Purcell effect enhancement on the quantum efficiency varies.Index Terms-Light-emitting diodes, non-polar GaN, photonic crystal, purcell effect.

Design of photonic crystals for light‐emitting diodes

“…The Purcell effect can be used to control the spontaneous radiation frequency of the LED, thus improving the LEE and modulation bandwidth of the LED. 3,33 When multiple "microcavities" are introduced, the coherent coupling between the light emitted from multiple resonant cavities can achieve the beam collimation effect, so that the light emitted from the LED has a smaller radiation angle (directional radiation) and higher brightness. 25,45 Many scholars have used defect states to modulate LEDs so that photonic crystals act as color conversion layers or as fluorescent materials in LEDs, which improves the luminescent color of LEDs and improves the problem of poor monochromaticity of LEDs.…”

“…This almost “microcavity” (MC) structure can improve LED light directionality, efficiency, and color coordination by filtering a particular frequency wave. The Purcell effect can be used to control the spontaneous radiation frequency of the LED, thus improving the LEE and modulation bandwidth of the LED 3,33 . When multiple “microcavities” are introduced, the coherent coupling between the light emitted from multiple resonant cavities can achieve the beam collimation effect, so that the light emitted from the LED has a smaller radiation angle (directional radiation) and higher brightness 25,45 .…”

“…LED applications exhibit a wide range of potential and serve as an indispensable source of illumination. [1][2][3][4] The internal quantum efficiency (IQE) of typical visible LEDs is now very close to being equivalent to 100%. On the other hand, because of the high refractive index of the material that is used to make LEDs, there is total internal reflection (TIR).…”

“…LEDs find predominant utilization in four key domains of application, namely liquid crystal display (LCD) backlighting, display technology, transportation lighting, and general illumination. LED applications exhibit a wide range of potential and serve as an indispensable source of illumination 1–4 . The internal quantum efficiency (IQE) of typical visible LEDs is now very close to being equivalent to 100%.…”