Improved light output of GaN-based vertical light emitting diodes using SiO2 nanotube arrays and transparent metal oxide current conduction layer

Abstract

The use of a refractive index matching (RIM) structure with indium zinc oxide (IZO) transparent conduction layer and SiO2 nanotube (SiO2-NT) arrays to improve light extraction of vertical structure KOH-etched GaN-based light emitting diodes (VLEDs) is demonstrated. Compared to regular VLED with KOH-roughened surface, it shows considerable gains in light emitted critical angle and light output power by 21.3° and 103% at 350 mA, respectively. These improvements could be attributed to the effectiveness of the IZO/SiO2-NT RIM scheme in ameliorating current crowding and significantly minimizing the total internal reflection effect.

Enhanced light-extraction from hierarchical surfaces consisting of p-GaN microdomes and SiO2 nanorods for GaN-based light-emitting diodes

“…[5][6][7][8] (ii) When the structure feature is smaller than the incident wavelength, it could serve as an effective medium with gradient refractive index from semiconductor to air, thus efficiently enhancing light extraction and extending the critical angle. 9 Light-extraction enhancement based on such mechanism has been demonstrated on InGaN LEDs using ZnO nanotips, 10 Si nanotubes, 11 and GaN surface roughing. [12][13][14] A concept employing hierarchical structures combining both the large (microscale) and small (nanoscale) structures is expected to realize the optimal photon management for enhancing the light-extraction of LEDs and the light-trapping capability of solar cells.…”

GaN-Based Multiple-Quantum-Well Light-Emitting Diodes Employing Nanotechnology for Photon Management

“…The light output power of NC-LEDs and NR-LEDs are greater than that of a conventional LED by 109.9% and 60.6% at 20 mA, respectively [45]. Nanostructures using SiO 2 have been also proposed [17], [48].…”

“…To the best of our knowledge, no clear model of exact control of radiation pattern has been proposed. However, we can conclude from the preceding literature that the surface texture with high aspect ratio such as NRs will result in a more collimated radiation pattern [14]- [17]. The concentrated light at normal direction can be attributed to the waveguiding effect of the rodlike nanostructure.…”

Enhanced light output of vertical GaN-based LEDs with surface roughened by refractive-index-matched Si3N4/GaN nanowire arrays

“…, where n 1 is the refractive index of GaN (n = 2.5), 20) n 2 is the refractive index of the epoxy (n = 1.38-1.58), 21) and n opt is 1.85-1.98. The refractive index of the Si 3 N 4 film (n = 1.97) obtained using PECVD thus suffices for this optimization.…”