Piezoelectric Field Effect and Field-Effect Transistors Based on MoSi22N4, MoSi2P4, and MoGe2N4 Monolayers

This study provides a comparative analysis of piezoelectric and conventional field-effect transistors (FETs) designed with monolayers of MoSi2N4, MoSi2P4, and MoGe2N4. The electronic parameters such as bandgaps, energy band edges, and electron effective masses under the influence of out-of-plane compressive stress, as well as the inherent stiffness of materials, are meticulously evaluated using the framework of density functional theory (DFT). Our research illustrates that vertical compressive stress has a more pronounced effect on the conduction band minimum (CBM) compared with the valence band maximum (VBM), positioning these novel 2-D materials as promising candidates for the channel of n-type piezoelectric FETs. The effects of stress on the piezoelectric FET channel is investigated, and the current–voltage ( ${I}-{V}$ ) characteristics are analyzed using the nonequilibrium Green's function (NEGF) formalism. This study reveals that devices engineered with these 2-D materials showcase an ${I}_{\text {on}}/{I}_{\text {off}}$ ratio surpassing 106 and a subthreshold swing (SS) in the vicinity of 60 mV/dec. Compared with their conventional counterparts, piezoelectric FETs using these examined materials demonstrate superior operational performance, with MoSi2N4-based piezoelectric FET boasting the optimal ${I}_{\text {on}}/{I}_{\text {off}}$ and the least SS.