Geometrical stability, electrical properties, and device applications of various <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"> <mml:msub> <mml:mrow> <mml:mi>Mo</mml:mi> <mml:mi>Si</mml:mi> </mml:mrow> <mml:mn>2</mml:mn> </mml:msub> <mml:msub> <mml:mrow> <mml:mrow> <mml:mi mathvariant="normal">N</mml:mi> </mml:mrow> </mml:mrow> <mml:mn>4</mml:mn> </mml:msub> </mml:math> derivatives and their heterojunctions

Abstract

The recently emerging ${\mathrm{Mo}\mathrm{Si}}_{2}{\mathrm{N}}_{4}$ monolayer has attracted great attention due to its excellent electronic properties. Here, various ${\mathrm{Mo}\mathrm{Si}}_{2}{\mathrm{N}}_{4}$ derivatives and related heterojunctions are proposed, and their structural stability, electronic properties, and potential applications are studied systematically. Ten monolayer derivatives are obtained by the layer-by-layer etching simulations. Upon the assessment of energetic, thermodynamic, dynamic, and mechanical stability, we find that eight derivatives are stable, behaving as semiconductors, metals, and a bipolar magnetic semiconductor, respectively. Particularly, the five stable metallic derivatives are combined with semiconducting parent ${\mathrm{Mo}\mathrm{Si}}_{2}{\mathrm{N}}_{4}$ to construct two-dimensional metal-semiconductor van der Waals heterojunctions (vdWHs), in which two vdWHs are structurally stable, with extremely low intrinsic Schottky barrier height and Ohmic contact, respectively, favorably to electron injection in devices. Based on such stable vdWHs, we design various high-performance field effect transistors (HPFETs), and the combined effects of various factors such as gate dielectric material, underlap length, and doping concentration are considered. Interestingly, it is found that the subthreshold swing for four FETs is lower than the thermodynamic limit (60 mV/dec), breaking through ``Boltzmann tyranny'' restricting traditional semiconductor devices, and for most of the suggested FETs, their current on-off ratios reach ${10}^{3}$ order, satisfying the orders of magnitude requirement of the on-off ratio in the International Technology Roadmap for Semiconductors standard. This study not only predicts the stability and outstanding electronic properties of ${\mathrm{Mo}\mathrm{Si}}_{2}{\mathrm{N}}_{4}$ derivatives and related heterojunctions, but also indicates that those stable vdWHs are promising candidates for developing HPFETs with low-power consumption.

Topics & Concepts