Theoretical studies of electronic transport in two-dimensional materials for transistor applications

There has been a wide interest in two-dimensional (2D) materials for their application as the channel in transistors, due to their ability to confine carriers to atomically thin layers, providing excellent electrostatics and reduced short-channel effects. However, there is a large discrepancy among the theoretical predictions of their transport properties in the literature. Given this state of uncertainty, we critically review the models employed, considering phosphorene, silicene and germanene as examples, and provide, what we believe is a more realistic model to evaluate the transport properties. We evaluate low- and high-field transport characteristics for these materials using Monte Carlo method, employing full bands and electron-phonon matrix elements. We find that the mobility obtained for phosphorene does not exceed 25 cm2/V·s, contrary to high mobilities predicted in the literature. In the case of silicene and germanene, we find that the lack of horizontal mirror (σh) symmetry in these 2D crystals results in divergence of the electron/ZA-phonons coupling at small wavevectors. By providing a cutoff for the ZA phonons, we obtain relatively large electron mobilities of 701 cm2V−1s−1 for silicene and 2327 cm2V−1s−1 for germanene. We then extend our model to simulate a 2D material based field effect transistor (FET), considering phosphorene as the channel. Despite phosphorene having a low electron mobility, we find the the performance of its device is comparable to other devices simulated with similar dimensions.