Enhanced Zero-Bias Rectification in 1D Metal-Double-Insulator-Graphene Diodes for RF Energy Harvesting

Passive rectifiers in radio frequency (RF) energy-harvesting applications require viable zero-bias responsivities to achieve significant RF-to-DC conversion efficiencies. While conventional metal-insulator-metal (MIM) diodes have been widely studied for high-frequency rectification, they often exhibit suboptimal zero-bias performance. Here, we demonstrate enhanced performance by modifying three key features of MIM diodes. We fabricated diodes with a second insulating layer, used graphene as one of the contacts, and formed a one-dimensional (1D) junction along the edge of graphene. The resulting 1D metal-double-insulator-graphene (MIIG) diode with TiO₂ and Ta₂O₅ insulators shows excellent zero-bias responsivity of up to 9.7 A/W. Our model indicates that this is due to a mix of thermionic emission at the 1D junction, modulation of the graphene work function toward a lower transport barrier, and trap-assisted transport through Ta₂O₅. These results are essential for the development of high-efficiency rectennas for RF energy-harvesting applications.