CVD-Grown Monolayer Graphene-Based Geometric Diode for THz Rectennas

Abstract

For THz rectennas, ultra-fast diodes are required. While the metal–insulator–metal (MIM) diode has been investigated in recent years, it suffers from large resistance and capacitance, as well as a low cut-off frequency. Alternatively, a geometric diode can be used, which is more suitable due to its planar structure. However, there is only one report of a THz geometric diode based on a monolayer graphene. It is based on exfoliated graphene, and thus, it is not suitable for mass production. In this work, we demonstrate chemical vapor deposition (CVD)-grown monolayer graphene based geometric diodes, which are mass-producible. The diode’s performance has been studied experimentally by varying the neck widths from 250–50 nm, the latter being the smallest reported neck width for a graphene geometric diode. It was observed that by decreasing the neck widths, the diode parameters such as asymmetry, nonlinearity, zero-bias resistance, and responsivity increased within the range studied. For the 50 nm neck width diode, the asymmetry ratio was 1.40 for an applied voltage ranging from −2 V to 2 V, and the zero-bias responsivity was 0.0628 A/W. The performance of the diode was also verified through particle-in-cell Monte Carlo simulations, which showed that the simulated current-voltage characteristics were consistent with our experimental results.

Simulation of Z-Shaped Graphene Geometric Diodes Using Particle-in-Cell Monte Carlo Method in the Quasi-Ballistic Regime

“…For these parameters, electrons are the majority carriers, and their concentration is . The effective mass, , follows the relation, where h is Planck’s constant, and is the electron mass [ 18 ]. For these simulations, this gives .…”

“…In a recent study by Wang et. al, an inverse-arrowhead diode was fabricated and measured with results showing correspondence to the simulator [ 18 ].…”

Progress in THz Rectifier Technology: Research and Perspectives

“…Second, the exfoliated graphene is not uniform; therefore, some areas of its surface, may be multi-layer rather than monolayer. In [ 86 ], the authors present a CVD-grown monolayer graphene-based geometric diode for THz rectennas. This process allows realizing rectennas at a mass scale.…”

“…This technology is still in its infancy and several limitations are waiting to be overcome. For example, for rectification to occur, charge carriers must travel ballistically (MFPL greater than device size) or quasi-ballistically (MFPL close to device size) [ 86 , 87 ] through the material, which requires that the sizes of the device should be approximately MFPL or lower. This places stringent manufacturing requirements on conventional metal-based devices, where typical mean-free-path lengths are less than 100 nm.…”

“…The second area of investigation is the selection of new materials because as the frequency increases, metals become very resistive. The results obtained using this type of diode around 30 THz are more encouraging [ 86 , 87 , 97 , 98 , 99 , 100 , 101 , 102 , 103 ].…”