OFF-state current limits of narrow bandgap MOSFETs

OFF-state current limitations of two types of MOSFETs, namely 1) flatband-mode MOSFET and 2) inversion-mode MOSFET, with narrow bandgap channel materials such as InSb, InAs, InGaAs, and Ge are discussed in conjunction with long-term requirements of the International Technology Roadmap for Semiconductors (ITRS). Flatband-mode high-mobility MOSFETs appear to be better suited for low OFF-state currents, in particular when a backside contact is used for minority carrier extraction. Based on OFF-state thermal minority carrier generation in narrow bandgap materials at room temperature, Hatband MOSFETs with InSb channels appear to be applicable for highperformance logic and even low operating power requirements of the long-term ITRS; however, standby power requirements will demand InAs or channels of higher bandgap unless material and interface quality (and, thus, carrier lifetime) is substantially improved. The effects of drain-induced barrier lowering, band-to-band tunneling, impact ionization, and increased temperature on OFF-state currents are not considered here but may impose further restrictions.