Ag-mesh-combined graphene for an indium-free current spreading layer in near-ultraviolet light-emitting diodes

Abstract

We have designed and fabricated Ag-mesh-combined graphene current spreading layers (CSLs) for GaN-based near-ultraviolet light-emitting diodes (NUV LEDs). Three different types of the CSLs were fabricated having 300 μm, 150 μm, and 75 μm gaps between the mesh lines. Optical and electrical properties were investigated and the performance of the LEDs having the CSLs and were compared with those of LEDs having indium tin oxide and graphene CSLs. The light output power of the LEDs with the Ag-mesh-combined graphene CSL adopting 150 μm-gap was highest at both the same current injection and at the same input power. This was possible due to the lowering of the sheet resistance via the adoption of an Ag mesh and the networking of the Ag mesh using a graphene sheet with very little transmittance loss.