An MoS2-Based Piezoelectric FET: A Computational Study of Material Properties and Device Design

In this paper, we show that MoS
₂
multilayers have mechanical and electrical properties that qualify them as promising channel materials for an n-type piezoelectric FET (PZ-FET). We present extensive density functional theory calculations to investigate the effects of a compressive, out-of-plane stress on MoS
₂
monolayers and multilayers and extract the corresponding stiffness, as well as the sensitivity to stress of the conduction and valence band edge, and of the effective masses. Then, we use these material properties and a top-of-the-barrier ballistic transistor model to evaluate numerically the IDS versus V
_G
characteristics of n-type PZ-FETs with an MoS
₂
channel material. Our results indicate that MoS
₂
multilayers are the best material option for n-type PZ-FETs, which can reach a subthreshold swing of about 40 mV/decade for a 5-nm-thick piezoelectric layer. This is because the weak interlayer van der Waals bonding makes the conduction band edge in MoS
₂
multilayers very sensitive to vertical compressive stress. The simulated MoS
₂
PZ-FETs exhibit large ION/IOFF ratios at low voltage and have better subthreshold steepness compared with the counterpart device employing a 3-D semiconductor.