Thermal transport and application reassessment of 2D MSi <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si94.svg" display="inline" id="d1e908"> <mml:msub> <mml:mrow/> <mml:mrow> <mml:mn>2</mml:mn> </mml:mrow> </mml:msub> </mml:math>

The two-dimensional MA2Z4 materials are proposed as suitable replacements for silicon channels in field-effect transistors (FETs). In the present work, the ThSi2N4 and CeSi2N4 monolayers from the family, with robust ambient stabilities are thermally investigated using the non-equilibrium Monte Carlo simulation of the phonon Boltzmann transport equation. In particular, the ThSi2N4, has a very appropriate electron mobility, being the highest among all the stable MA2Z4 monolayers. Here, the reliability of the MOSFET with the Th(Ce)Si2N4 channel has been reassessed and determined to be low due to the high maximum temperature achieved. Accordingly, the phonon analysis is performed for both monolayers and consequently it revealed that the dominant contribution of the fast and energetic LA and also slow and low energy ZA phonons alongside the minor participation of the TA phonons is responsible for the peak temperature rise reaching 800 and 600 K, respectively, for ThSi2N4 and CeSi2N4 2D layers. This finding presents that the ThSi2N4 monolayer, is not thermally the most suitable candidate for replacing as the silicon channel but alternatively is capable of generating a significant temperature gradient, which could be one of the factors favoring the use of this material for the thermoelectric generators.