$\hbox{Ge-Si}_{x}\hbox{Ge}_{1 - x}$ Core–Shell Nanowire Tunneling Field-Effect Transistors

Abstract

We report the fabrication and experimental investigation of Ge-Si <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</i> Ge <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1-</sub> <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</i> core-shell nanowire (NW) tunneling field-effect transistors (TFETs), consisting of p-i-n device structures realized by low-energy ion implantation. We investigate the NW TFET device characteristics as a function of drain doping, channel length, and temperature. Our devices show on-state currents of up to <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">I</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ON</sub> ~ 5μA/μm, with an ambipolar behavior that can be suppressed by varying the drain doping concentration. The subthreshold swing of NW TFETs shows little temperature dependence down to 77 K, consistent with band-to-band tunneling as being the dominant carrier injection mechanism.