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 disper­sion 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.