Nanoscale Ni/Au wire grids as transparent conductive electrodes in ultraviolet light-emitting diodes by laser direct writing

Laser direct writing was applied for fabricating Ni/Au wire grid structure as transparent conductive electrode (TCE) of near ultraviolet (UV) light-emitting diodes (LEDs). Effect of period of Ni/Au wire grid on optical and electrical properties of UV LED was investigated. At the same wire width nearly 600 nm, the UV LED with small period of Ni/Au wire grid showed higher light output power (LOP) and lower forward voltage due to the lower sheet resistance and more uniform current spreading. Compared to Ni/Au wire grid, the UV LED with Ni/Au thin film TCE showed higher LOP and lower forward voltage because of better current spreading, which indicated that current spreading was more important than the light absorption of the metal materials. In addition, the UV LED with indium tin oxide (ITO) TCE exhibited a higher LOP than that of UV LED with Ni/Au thin film because of the high transmittance of ITO, which revealed that the transparency of material played a major role in improving the LOP when the Ni/Au thin film and ITO exhibited a similar current spreading.