Modeling & Simulations of Advanced MOSFETs

  As feature size of conventional planar metal-oxide-semiconductor field-effect transistor (MOSFET)  shrinks into the nanometer regime, performance of devices is degraded due to short-channel effects caused by weakened gate control. To overcome this, devices in new structure such as ultra-thin body (UTB), FinFET, nanowire (NW) have emerged. In single nanometer regime, however, semi-classical analysis of such devices is unreliable. Therefore, atomistic level approaches are required. In our laboratory, we develop quantum simulator for devices such as UTB, NW transistors and research by using the results of quantum simulation.

 Silicon nanowire field-effect transistors (Si NWFETs) with multiple gates around the silicon channel that can significantly improve the gate control are therefore considered to be promising candidates for the next generation transistors and have drawn considerable attention recently. In addition to the effective suppression of short channel effects, the SNWFETs with multiple gates show excellent current drive and they are also compatible with conventional CMOS processes.

  Negative capacitance FETs (NCFETs) are one of candidates for steep slope devices. NCFETs are similar to conventional MOFSETs, but the gate insulator in conventional MOFSETs is replaced by ferroelectric. Unlike other steep slope devices, NCFETs can achieve high on current and low sub-threshold swing amplifying gate bias through ferroelectric. Landau equation is used to evaluate ferroelectric and transport of the devices is considered by quantum transport simulation

  2DMs have been focused due to their structural and electronic properties. Their weak interlayer interaction can mitigate surface roughness scattering, which is a dominant scattering in UTB FETs.

  2DMs that we are currently interested in are summarized below.

  • Transition metal dichalcogenides (TMDs, MX2)
  • Black phosphorus (phosphorene, BP)

  Graphene, which is a representative one of 2DMs, has ultra-high mobility. However, its zero bandgap is a big obstacle to gaining high ON/OFF current ratio for transistor operation. Unlike graphene, TMDs and BP have inherent non-zero bandgap, thus, they have great potential for future electronic devices. We analyze properties of the 2DMs in atomistic level, and estimate performance  of 2DM-based devices by quantum transport simulation.