Graphene-based transparent conductive electrodes for GaN-based light emitting diodes: Challenges and countermeasures

Abstract

Graphene, with attractive electrical, optical, mechanical and thermal properties, is considered to be an ideal candidate for transparent conductive electrodes (TCEs) in many optoelectronic devices, including III-nitride based devices. However, high contact resistivity (ρc) between graphene and GaN (especially p-GaN) has become a major challenge for graphene TCEs utilization in GaN-based light-emitting diodes (LEDs). Here, we analyzed the graphene/GaN contact junction in detail and reviewed the current research progress for reducing ρc in graphene TCEs on GaN LEDs, including interface engineering, chemical doping and tunnel junction design. We also analyzed the current diffusion length for a single layer graphene (SLG) and multiple layer graphene (MLG) TCEs. Finally, to improve the fabrication process compatibility and simplicity with paramount reproduction, a method of directly growing graphene films on GaN by chemical vapor deposition (CVD) is proposed. We also give a short analysis on the reliability of graphene TCEs for GaN-based LEDs. It is believed that this is the ultimate solution for graphene TCEs application for GaN-based LEDs and others in general for other opto- and electrical devices.