Novel vertically stacked Ge_0.85Si_0.15nGAAFETs above a Si channel with low SS of 76 mV/dec by underneath Si channel and enhancedI_on(1.7X atV_OV=V_DS= 0.5 V) by Ge_0.85Si_0.15channels

Abstract

An engineering solution is provided to improve the electrostatic behaviors of Ge-based channels gate-all-around FETs. We demonstrate the vertically stacked Ge 0.85 Si 0.15 channels above a Si channel, which has good subthreshold behaviors. The two Ge 0.85 Si 0.15 channels are tensily strained to improve I on . With optimized channel dimensions, the threshold voltage of Ge 0.85 Si 0.15 channels is more positive than the Si channel by quantum confinement. Therefore, the underneath Si channel with good electrostatic control dominates the subthreshold region. Good subthreshold slope=76 mV/dec and low drain-induced barrier lowering=36 mV/V are achieved. For on-state, the stacked high-mobility GeSi channels turn on after the Si channel to achieve I on of 13.9 μA per stack at V OV =V DS =0.5 V.