Performance Projections for Two-dimensional Materials in Radio-Frequency Applications

Given the immense attraction of using two-dimensional materials for high-frequency applications, there is a critical need for computational models that aid the production of high-frequency performance projections based on their material properties. In this work, we use the atomistic nonequilibrium Green’s function approach to predict the performance of ballistic radio-frequency transistors based on a broad range of two-dimensional semiconducting materials, including $\mathrm{Mo}{\mathrm{S}}_2$, ${\mathrm{WS}}_2$, ${\mathrm{WSe}}_2$, and phosphorene. Self-consistent ballistic quantum-transport simulations are performed on monolayer transistors with a 15-nm gate length and an effective gate-oxide thickness of 0.44 nm. We show that rather than the bandgap, the effective mass and the dielectric constant significantly influence the unity current gain cutoff frequency ($f_t$), the maximum oscillation frequency ($f_{\text{max}}$), and the intrinsic gain ($G_{\text{int}}$). Phosphorene with a low effective mass and high dielectric constant is found to be the most promising material with $f_t\simeq 10\mathrm{THz}$, $f_{\text{max}}\simeq 6\mathrm{THz}$, and $G_{\text{int}}\simeq 100\text{℧}/\text{℧}$. Results are further corroborated analytically using the Wentzel-Kramers-Brillouin approximation and also benchmarked with previous reports. Furthermore, the effect of extrinsic parameters, such as Schottky barrier height and strain on $f_t$ and $f_{\text{max}}$, is discussed. This study can thus be used as a comprehensive, physics-based search guide of two-dimensional materials for radio-frequency applications.