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, flatband MOSFETs with InSb channels appear to be applicable for high-performance 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