The impact of the ring shaped valence band in few-layer iii-vi materials on fet operation

Mexican hat shaped dispersions are relatively common in few-layered two-dimensional materials. In one to four monolayers of the group-ill chalcogenides (GaS, GaSe, InS, InSe) the valence band undergoes a band inversion from parabolic to a Mexican hat dispersion [1]. This Mexican hat dispersion results in a singularity in the density of states at the band edge. This enhances the thermo electric properties, however the effect on field effect transistor performance has not yet been investigated. To evaluate the impact of this ring shaped disperision on FET performance, we use a top of the barrier FET model. The physical gate length, effective oxide thickness and power supply voltage for the simulated devices are 12.8 nm, 0.68nm, and 0.3V respectively, following the low-voltage parameters described by Nikonov and Young [2]. The simulated device is shown in Fig. 1. To model the electrostatic potential along the channel of the device we solve a 2-D Poisson equation over the simulation domain. The density of states and density of modes calculated from the Mexican hat dispersion described in Ref. [I] are shown in Figs. 2 and 3, respectively. The density of modes is used as input for the current calculation. The performance characteristics of the devices are benchmarked using the 15nm node low- voltage criteria defined by Nikonov and Young [2] and compared to other devices.