The Light Extraction Efficiency of p-GaN Patterned InGaN/GaN Light-Emitting Diodes Fabricated by Size-Controllable Nanosphere Lithography

Abstract

The authors present a light extraction improvement at a low operation voltage from p-GaN patterned InGaN/GaN light-emitting diodes (LEDs) fabricated using size-controllable nanosphere lithography and subsequent inductively coupled plasma etching. A 300-nm polystyrene (PS) nanosphere array was used as an etching mask in order to produce ordered pillar patterns on the p-GaN layer, during which the top and bottom size of the pillars were tailored to optimize the electrical and optical properties by varying the diameter of the PS nanosphere masks. Three LEDs, without patterns and with pillar patterns of 210 nm and 240 nm diameter, were compared with each other, in which the LED with 240 nm diameter pillar patterns showed the highest output power (32.6% higher than that of the LEDs without patterns) in both its electroluminescence and photoluminescence measurements.

Tuning a nano-pillar array for enhancing the photoluminescence extraction efficiency of GaN-based light-emitting diodes

“…Assuming that the output power from the side wall and back side is neglected, only about 4% of the light generated in the multiple quantum well (MQW) can escape into the surrounding space. [8] Various methods have been proposed to increase the extraction efficiency, such as surface patterning techniques, [9][10][11][12][13][14][15] inclined side-wall etching, [16,17] and patterned sapphire substrate (PSS). [18,19] Among these approaches, surface patterning is one of the most efficient methods to provide a large enhancement factor of the LEE, due to the increased scattering rate at the roughened surface.…”

Automated SEM Image Analysis of the Sphere Diameter, Sphere-Sphere Separation, and Opening Size Distributions of Nanosphere Lithography Masks

“…Nanosphere lithography (NSL) provides a cost-effective method to fabricate periodic nanopatterns on large surface areas (Hulteen & Van Duyne, 1995; Boneberg et al, 1997; Haginoya et al, 1997; Burmeister et al, 1999). Regular arrays have a great potential for applications, for example, in optoelectronics (Sim et al, 2011; Zhang et al, 2013), electrochemical sensors (Purwidyantri et al, 2016), optical fiber tip nanoprobes (Pisco et al, 2017), and as metamaterials (Gwinner et al, 2009). Recently, it has been demonstrated that NSL masks can be fabricated in roll-to-roll processes, opening the path to industrial scale applications (Chen et al, 2020).…”

Effects of Nanosized Ni Particle Structure on the Enhancement of Light Extraction from 600 nm AlGaInP Light-Emitting Diodes

“…2) Research showed that the optical output power of lightemitting diodes can be significantly improved by enhancing the light extraction efficiency. [3][4][5][6][7][8][9][10][11][12][13][14][15] However, the light extraction efficiency for LEDs is still low. The refractive indices of semiconductors are usually high, making the critical angle for the total internal reflection (TIR) between the semiconductor/air interface small.…”

“…7) Additionally, nanometer-scale photonic crystal structures to improve the light extraction from GaN LEDs [8][9][10][11] and AlGaInP LEDs 12) have been reported. GaN-based LEDs with holographically fabricated concave hemisphere-shaped patterning on indiumtin-oxide layer 13) and p-GaN-patterned InGaN/GaN LED fabricated by size-controllable nanosphere lithography 14) have also been investigated. The use of colloidal method for achieving self-assembled microlens arrays had also been reported leading to significant increase in light escape cone and light extraction efficiency in III-nitride LEDs.…”