ITO/Ag/AlN/Al2O3 multilayer electrodes with conductive channels: Application in ultraviolet light-emitting diodes

Abstract

There have been considerable efforts to use oxide/metal/oxide (OMO) multilayers as transparent conductive electrodes (TCEs) for various optoelectronic devices. However, it was difficult to achieve high transmittances in the UV region because relatively narrow-bandgap oxide films such as indium tin oxide (ITO) and ZnO have been used to achieve low series resistances. In this study, ITO/Ag/AlN/Al2O3-based TCEs were fabricated by incorporating conductive channels in AlN/Al2O3 wide-bandgap bilayers under electric fields. These multilayered films exhibited much higher transmittances in the UV region and lower sheet resistances compared to the reference ITO and ITO/Ag/ITO electrodes. These films were then applied in GaN-based near-UV LEDs, following the investigation of ohmic conduction mechanisms at the interface between p-GaN and ITO/Ag/AlN/Al2O3 TCE layers. The LEDs with ITO/Ag/AlN/Al2O3 multilayers exhibited much lower forward voltages and higher output powers than those of the other two LEDs. This method offers a new and effective route to enhance the transmittance of OMO-based TCEs at a shorter wavelength without losses in electrical conductivity. (C) 2018 Elsevier B.V. All rights reserved.