Nitride‐Based Microlight‐Emitting Diodes Using AlN Thin‐Film Electrodes with Nanoscale Indium/Tin Conducting Filaments

• Published in: Small (Weinheim an der Bergstrasse, Germany) Germany), 2018-12, Vol.14 (49), p.e1801032-n/a
• Main Authors: Son, Kyung Rock, Lee, Tae Ho, Lee, Byeong Ryong, Im, Hyun Sik, Kim, Tae Geun
• Format: Article
• Language: English
• Subjects: Aluminum nitride; Conduction; Current injection; Diodes; Electrodes; Electroluminescence; Emission; Filaments; fill factor; Indium tin oxides; Injection current; microlight‐emitting diodes; nanoscale conducting filament; Nanotechnology; Organic light emitting diodes; Schottky barrier height; Thin films; Tin; Transmission electron microscopy; transparent conducting electrode
• ISSN: 1613-6810; 1613-6829
• DOI: 10.1002/smll.201801032

Microlight‐emitting diodes (µLEDs) are emerging solutions for both high‐quality displays and lighting technologies. However, the overall light output power density of these devices is low, as the emission area is shielded by the p‐electrodes required for current injection. In this study, instead of the more conventionally used indium tin oxide (ITO), an AlN thin film with nanoscale conducing filaments (CFs) is used, referred to as CF‐AlN, as a transparent conducting electrode (TCE), to enhance the output power density from the same emission area. As a result of this modification, the electroluminescence intensity is enhanced by 10% at an injection current of 10 mA, and the current density is improved by 13% at a forward voltage of 4.9 V, in comparison to the parameters observed with ITO‐based µLEDs. This improvement is attributed to the higher transmittance of CF‐AlN TCEs, together with efficient hole injection from the p‐electrode into the light‐emitting layer, through the CFs formed in the AlN layer. In addition, using transmission electron microscopy analyses, the origin of the CFs is directly identified as the diffusion of In and Sn ions, which provides critical insight into the conduction mechanism of AlN‐based TCEs. A rod‐shaped AlN thin film with In/Sn‐based nanoscale conducting filaments is used as the p‐type transparent conductive electrode (TCE) of microlight emitting diodes, to improve the fill factor (by enhancing the light emission) and the current density (by improving the Ohmic behavior due to the reduced Schottky barrier height through the inclusion of conducting filaments at the AlN TCE/p‐GaN interface), simultaneously.