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

Abstract

A surface roughening scheme with Si3N4-coated GaN nanowire (NW) arrays is proposed to improve the light extraction efficiency of GaN-based vertical light-emitting diodes (VLEDs). The scheme allows a graded refractive index that varies from 2.5 (GaN) to 1.9–2.0 (Si3N4) to 1 (air). Experimental results show that the use of 0.8-µm-long GaN NW arrays coated with a 250-nm-thick Si3N4 film enhances the light output power by 28.7% at 350 mA compared with that of regular VLEDs with a KOH-roughened surface. This enhancement is attributed to the Si3N4/GaN NW arrays effectively releasing total internal reflection and minimizing Fresnel loss.

Improving Crystalline Silicon Solar Cell Efficiency Using Graded-Refractive-Index SiON/ZnO Nanostructures

“…The simulation results shown in Figure 7 demonstrate an LTE improvement trend that is similar to those obtained in the experimental findings. To further clarify the effectiveness of the surface roughening schemes, the light absorption efficiency of SCs with micropyramids, ZnO NW arrays atop the micropyramids, ZnO NT arrays atop the micropyramids, and SiON/ZnO NT arrays atop the micropyramids was simulated using Tracepro [7]. The results are shown in Figure 7.…”

“…Surface roughening through the chemical wet etching process [1,2], nanoimprint lithography [3], and nanostructures [4,5] has been applied to roughen the top surface of optoelectronic devices. Surface roughening has attracted considerable interest for applications such as solar cells (SCs), light-emitting diodes (LEDs), ultraviolet photodetectors (UV-PDs), and gas sensors [6][7][8][9]. A suitably roughened surface can significantly improve the surface reflectivity of SCs, alleviate the total internal reflection of LEDs, and increase the responses of UV-PDs and gas sensors [6][7][8][9].…”

“…Surface roughening has attracted considerable interest for applications such as solar cells (SCs), light-emitting diodes (LEDs), ultraviolet photodetectors (UV-PDs), and gas sensors [6][7][8][9]. A suitably roughened surface can significantly improve the surface reflectivity of SCs, alleviate the total internal reflection of LEDs, and increase the responses of UV-PDs and gas sensors [6][7][8][9]. However, most surface roughening methods involve expensive lithographic patterning or cumbersome fabrication processes and can even deteriorate electrical properties, making them unsuitable for mass production.…”