Phonon limited transport in graphene pseudospintronic devices

Abstract

Abstract-A predicted room-temperature phase transition from Fermi liquid to dissipationless Bose-Einstein exciton superfluid suggests that graphene pseudospin devices may have the potential to far outperform traditional CMOS devices. When examining the possibility of a room-temperature exciton condensate, it is important to consider scattering of charge carriers by phonons in each of the constituent graphene monolayers. Using the nonequilibrium Green's function formalism, we examine the effect that carrier-phonon scattering has on device performance. We find that the effect of carrier-phonon scattering has strong dependence on the device coherence length. As such, for large gate voltages, the effect of phonons on interlayer transport is negligible.Index Terms-Critical current, nanoelectronics, phonons, tunneling. IT IS generally accepted that MOSFET scaling cannot continue unabated. In light of this, one of the most active areas of semiconductor electronics research is post-CMOS device technology. A variety of post-CMOS devices are under active consideration. In an effort to reach the smallest possible dimensions, molecular electronics has gained serious attention. While molecular electronics offers high device density and lowpower operation, issues surrounding the molecule-electrode coupling, low yield, and three-terminal device fabrication [1] plague development. Improvements in nanoscale fabrication techniques have sparked interest in replacing CMOS with nanoelectromechanical systems (NEMSs). NEMSs offer small leakage current and a large on-off ratio [2]; however, highfrequency switching speed and reliability remain unsolved challenges. Beyond these relatively exotic solutions, the tunnel field-effect transistor (TFET), whose operation is based on band-to-band tunneling [3], has shown much recent progress. TFETs showcase a low OFF-state current and a subthreshold slope experimentally demonstrated to be less than 60 mV/dec for carbon nanotube TFETs. However, TFETs also possess a low ON-state current, which must be significantly improved if these devices are to be implemented in information processing technologies. Graphene-based pseudospintronic (G-PsS) devices are predicted to exhibit a high ON-state current with low-power dissipation [4]- [6]. It has been proposed that G-PsS devices could outperform traditional CMOS as they operate based on coherent interlayer transport rather than on the principle of source injected charge based on thermionic emission. In some works, graphene-based pseudospin devices have been predicted to possess a room-temperature phase transition from normal Fermi liquid behavior to a Bose-Einstein condensate of indirectly bound excitons formed when electrons present in one layer bind with an equal number of holes in the other layer [7]-[9]. The transition temperature has not been theoretically resolved [10], and other works predict an orders-of-magnitude lower transition temperature [11]. Still, recent Coulomb drag experiments have provided evidence of the interlayer interactions which ...