Fabrication and Characterization of High-Efficiency Green InGaN Light-Emitting Diodes With Metal-Doped ITO Layer

We investigate a method to improve the efficiency of green InGaN light-emitting diodes (LEDs) using various metal-doped indium tin oxide (ITO) transparent contact layers. The resistance and transmittance of metal-doped ITO with different metal thicknesses and different rapid thermal annealing conditions were studied and analyzed systematically. It is found that extinction coefficient and surface roughness of ITO layer are distinctly reduced by doping suitable metal and annealing in a mixture of N
₂
/O
₂
(200:35) ambient at 600 °C for 3 min. In addition, it is useful to decrease the sheet resistance and provide more uniform current distribution by using the metal-doped ITO. Compared with conventional green LEDs with 80-nm ITO layer, there are an 18.9% increase in light-output power and a 1.5 V decrease in forward voltage at 120 mA for the green LEDs with 3-nm Al-doped ITO layer.