Material Selection for Minimizing Direct Tunneling in Nanowire Transistors

Somaia Sarwart Sylvia, University of California - Riverside
Hong-Hyun Park, Purdue University
M. Abul Khayer, University of California - Riverside
Khairul Alam, East West University
Gerhard Klimeck, Purdue University
Roger Lake, University of California - Riverside

Abstract

When the physical gate length is reduced to 5 nm, direct channel tunneling dominates the leakage current for both field effect transistors (FETs) and tunnel field effect transistors (TFETs). Therefore, a survey of materials in a nanowire (NW) geometry is performed to determine their ability to suppress the direct tunnel current through a 5 nm barrier. The materials investigated are InAs, InSb, InP, GaAs, GaN, Si, Ge and carbon nanotubes (CNTs). The tunneling effective mass gives the best indication of the relative size of the tunnel currents when comparing two different materials of any type. The indirect gap materials, Si and Ge, give the largest tunneling masses in the conduction band, and they give the smallest conduction band tunnel currents within the range of diameters considered. Si gives the lowest overall tunnel current for both the conduction and valence band and, therefore, it is the optimum choice for suppressing tunnel current at the 5 nm scale. A semi- analytic approach to calculating tunnel current is demonstrated which requires considerably less computation than a full-band numerical calculation.

Discipline(s)

Nanoscience and Nanotechnology