Comprehensive understanding of electron mobility and superior performance in sub-10 nm DG ML tetrahex-GeC₂ n-type MOSFETs

In this study, we have investigated the electron mobility of monolayered (ML) tetrahex-GeC2 by solving the linearized Boltzmann transport equation (BTE) with the normalized full-band relaxation time approximation (RTA) using density functional theory (DFT). Contrary to what the deformation potential theory (DPT) suggested, the ZA acoustic mode was determined to be the most restrictive for electron mobility, not the LA mode. The electron mobility at 300 K is 803 cm(2) (V s)(-1), exceeding the 400 cm(2) (V s)(-1) of MoS2 which was calculated using the same method and measured experimentally. The ab initio quantum transport simulations were performed to assess the performance limits of sub-10 nm DG ML tetrahex-GeC2 n-type MOSFETs, including gate lengths (L-g) of 3 nm, 5 nm, 7 nm, and 9 nm, with the underlap (UL) effect considered for the first two. For both high-performance (HP) and low-power (LP) applications, their on-state currents (I-on) can meet the requirements of similar nodes in the ITRS 2013. In particular, the I-on is more remarkable for HP applications than that of the extensively studied MoS2. For LP applications, the I-on values at L-g of 7 and 9 nm surpass those of arsenene, known for having the largest I-on among 2D semiconductors. Subthreshold swings (SSs) as low as 69/53 mV dec(-1) at an L-g of 9 nm were observed for HP/LP applications, and 73 mV dec(-1) at an L-g of 5 nm for LP applications, indicating the excellent gate control capability. Moreover, the delay time tau and power dissipation (PDP) at L-g values of 3 nm, 5 nm, 7 nm, and 9 nm are all below the upper limits of the ITRS 2013 HP/LP proximity nodes and are comparable to or lower than those of typical 2D semiconductors. The sub-10 nm DG ML tetrahex-GeC2 n-type MOSFETs can be down-scaled to 9 nm and 5 nm for HP and LP applications, respectively, displaying desirable I-on, delay time tau, and PDP in the ballistic limit, making them a potential choice for sub-10 nm transistors.