Formation of an indium tin oxide nanodot/Ag nanowire electrode as a current spreader for near ultraviolet AlGaN-based light-emitting diodes

Indium tin oxide (ITO) nanodots (NDs) were combined with Ag nanowires (Ag NWs) as a p-type electrode in near ultraviolet AlGaN-based light-emitting diodes (LEDs) to increase light output power. The Ag NWs were 30 ± 5 nm in diameter and 25 ± 5 μ m in length. The transmittance of 10 nm-thick ITO-only was 98% at 385 nm, while the values for ITO ND/Ag NW were 83%–88%. ITO ND/Ag NW films showed lower sheet resistances (32–51 Ω sq⁻¹) than the ITO-only film (950 Ω sq⁻¹). LEDs (chip size: 300 × 800 μ m²) fabricated using the ITO NDs/Ag NW electrodes exhibited higher forward-bias voltages (3.52–3.75 V at 20 mA) than the LEDs with the 10 nm-thick ITO-only electrode (3.5 V). The LEDs with ITO ND/Ag NW electrodes yielded a 24%–62% higher light output power (at 20 mA) than those with the 10 nm-thick ITO-only electrode. Furthermore, finite-difference time-domain (FDTD) simulations were performed to investigate the extraction efficiency. Based on the emission images and FDTD simulations, the enhanced light output with the ITO ND/Ag NW electrodes is attributed to improved current spreading and better extraction efficiency. (paper)