Hump Effects of Germanium/Silicon Heterojunction Tunnel Field-Effect Transistors

Abstract

The hump effects of germanium/silicon heterojunction tunnel field-effect transistors are discussed. Simulation results show that they are originated when indirect band-to-band tunneling is converted into direct one as gate voltage ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$V_{g}$ </tex-math></inline-formula> ) increases. In order to suppress the hump effects, two ideas are proposed. First, the length of intrinsic-germanium channel ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$L_{\mathrm{ Ge}}$ </tex-math></inline-formula> ) is optimized using a novel process flow. Second, gate-to-channel coupling is improved by increasing source doping concentration ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$N_{S}$ </tex-math></inline-formula> ).