Improved Light Extraction of GaN-Based Blue Light-Emitting Diodes with ZnO Nanorods on Transparent Ni/Al-Doped ZnO Current Spreading Layer

Abstract

We reported the light-extraction properties of InGaN/GaN multiple quantum wells blue light-emitting diodes (LEDs) with ZnO nanorod arrays (NRAs) on Ni/Al-doped ZnO (AZO) films as a current spreading layer (CSL). The Ni/AZO bilayer exhibited a high optical transmittance of ∼80% at λ∼460 nm. The electrical property of AZO films was improved by inserting a thin Ni layer, which leads to the better current–voltage characteristics of LEDs. The ZnO nanorods can be easily grown on the AZO surface of Ni/AZO CBL as the same materials by a simple wet chemical growth. For 450 ×450 µm2 LED with Ni/AZO CSL, the incorporation of ZnO NRAs into the AZO surface improved the light output power by ∼14% at 100 mA without causing any electrical degradation compared to the conventional LED without ZnO NRAs.

(Electronics and Photonics Division Award Address) Performance of InGaN/GaN-Based Light Emitting Diodes Fabricated with ZnO Nanorods

“…The increased light extraction due to the ZnO NRAs was attributed to the formation of sidewalls and a rough surface, causing a multiple photon scattering at the LED surface. Lee et al [16] investigated the light-extraction properties of blue LEDs fabricated with ZnO NRAs on Ni/Al-doped ZnO films. The ZnO NRAs were synthesized at 90 °C for 6 h in an aqueous solution.…”

“…Most of the previous results demonstrated the growth of ZnO nanorods that were not perfectly vertically aligned. Thus, unlike these previous works [12,16,19], in this study, a polymer-templated hydrothermal growth method [22] was used to grow perfectly aligned vertical ZnO NRAs. We investigated the effect of ZnO NRAs on the light output power and EQE electrical performance of InGaN-based LEDs, which were compared with those of LEDs with ITO-only electrode.…”