Sub-5-nm Monolayer GaSe MOSFET with Ultralow Subthreshold Swing and High On -State Current: Dielectric Layer Effects

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With the increasing demand for miniaturized devices and integrated circuits, ultrasmall-scale device units have attracted increasing attention. However, the short-channel effects severely limit the development of high-performance micro- and nanodevices. Here, we design sub-5-nm dual-gate monolayer $\mathrm{Ga}\mathrm{Se}$ metal-oxide-semiconductor field-effect transistors (MOSFETs) and systemically analyze the transmission spectrum, local density of states, on-state current (${I}_{on}$), and subthreshold swing (SS), considering different dielectric layer thicknesses, dielectric constants, and underlap lengths. The results show that, with decreasing equivalent oxide thickness, the SS (${I}_{on}$) shows a downward (uptrend) trend. Compared with ${\mathrm{Al}}_{2}{\mathrm{O}}_{3}$ and ${\mathrm{Hf}\mathrm{O}}_{2}$ substrates, the SS and ${I}_{on}$ can be modified obviously through the dielectric layer thickness for 3-nm $\mathrm{Ga}\mathrm{Se}$ MOSFETs with ${\mathrm{Si}\mathrm{O}}_{2}$ substrate. The ${I}_{on}$ can be tuned from 904 to 1766 \textmu{}A/\textmu{}m, which is about 2 times higher than the high-performance requirements of the International Technology Roadmap for Semiconductors (ITRS) (900 \textmu{}A/\textmu{}m) for 2028. Meanwhile, the SS is upgraded from 134.8 to 62.7 mV/dec, closing the Boltzmann tyranny (60 mV/dec). Therefore, this work provides a route to realize ultrashort-scale MOSFETs with an ultralow subthreshold swing and a high on-state current through engineering the dielectric layer.