Device and Circuit Lab

Ever-increasing power density in ICs, in which the metal-oxide-semiconductor field effect transistor is the basis of the highly integrated circuits, should be addressed to follow the Moore’s law. The exponential increase of power density arises from the Boltzmann limitation (i.e., the limitation of subthreshold slope of 60 mV/decade) of thermionic emission process operated semiconductor devices such as conventional MOSFETs or FinFETs. To overcome this, negative capacitance (NC) effect was first suggested in 2008 as a solution. Topological insulators (TIs) have received great attention because of their unique property, namely, bulk TI material is insulating; however, its surface is in a metallic state. This interesting property is due to the topological surface states (lying in the bulk energy gap) that are protected from scattering events with time-reversal symmetry. At the surface of a TI, there exist topological surface states and a two-dimensional gas (2DEG). As physical sizes of the transistors have been scaled down for decades, inevitable problems such as exponentially increasing power consumption and short channel effects hamper the miniaturization of semiconductor devices. As a breakthrough, a tunnel field effect transistor, which utilizes the band-to-band tunneling nature of carriers instead of thermionic emission process, was investigated as promising next-generation semiconductor device for low power operation.