Transfer-Free Patterned Graphene as a Transparent Electrode for Micro Light-Emitting Diodes

Micro light-emitting diode (LED) is one of the important research directions in the field of optoelectronics, and transparent electrodes with high conductivity and high transmittance play an important role in it. Graphene has excellent physical and chemical properties and has become one of the most potential transparent electrode materials. In this paper, transfer-free patterned graphene transparent electrodes were fabricated and applied to GaN-based micro LEDs. In this scheme, the Ni film is used as etching masks and graphene growth catalysts, simplifying the process flow and growing patterned graphene. The <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\text{SiO}_{2}$</tex> isolation layer prevents the fusion of p-type GaN and Ni at 600 <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">${}^{\circ}\mathrm{C}$</tex>, protecting the integrity of GaN and the catalytic performance of Ni. Both Ni and <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\text{SiO}_{2}$</tex> are removed by wet etching, and patterned graphene is prepared on the surface of GaN without transfer process. The results show that the multilayer graphene achieves good current expansion and transparency, and the micro LEDs fabricated exhibits good optical and electrical properties. The graphene prepared by this method avoids the potential damage to the graphene during the transfer process and the patterning process, and plays an excellent role as a transparent electrode on micro LEDs.