Performance Comparison of GaSb, Strained-Si, and InGaAs Double-Gate Ultrathin-Body n-FETs

摘要

Using a full-band and atomistic approach based on the nearest-neighbor tight-binding model and the nonequilibrium Green function formalism, $(hbox{111})/langlebar{hbox{1}} hbox{10}rangle$ GaSb, $(hbox{100})/langlehbox{110}rangle$ strained-Si, and $(hbox{100})/langlehbox{100}rangle$ $hbox{In}_{0.53}hbox{Ga}_{0.47}hbox{As}$ n-type double-gate ultrathin-body field-effect transistors designed according to the ITRS specifications for 2020 are simulated in the ballistic limit of transport and with electron–phonon scattering. It is found that, at an equivalent oxide thickness of 0.59 nm, the GaSb device offers the highest ballistic on-current at a fixed off-current, due to the projection to the $Gamma$ point of bands originating from the bulk $L$-valley and possessing a low transport effective mass. It is followed by the strained-Si FET and, finally, the $hbox{In}_{0.53} hbox{Ga}_{0.47}hbox{As}$ FET, the latter suffering from its small density of states in the channel despite very high electron velocities. However, when electron–phonon scattering is taken into account, the presence of multiple energy subbands, as in GaSb and strained Si, increases the probability of backscattering for electrons; thus, the current of these devices does not exceed that of the $ hbox{In}_{0.53}hbox{Ga}_{0.47}hbox{As}$ FET by more than 13%.