Self-Organized Ge Nanospherical Gate/SiO₂/Si_0.15Ge_0.85–Nanosheet n-FETs Featuring High ON-OFF Drain Current Ratio

We reported experimental fabrication and characterization of Si _0.15 Ge _0.85 n-MOSFETs comprising a gate-stacking heterostructure of Ge-nanospherical gate/SiO ₂ /Si _0.15 Ge _0.85 -nanosheet on SOI (100) substrate in a self-organization approach. This unique gate-stacking heterostructure is simultaneously produced in a single oxidation step as a consequence of an exquisitely controlled dynamic balance between the concentrations of oxygen, Si, and Ge interstitials at 900 °C. Process-controlled tunability of nanospherical gate of 60–100 nm in diameter, gate oxide thickness of 3 nm, and Si _0.15 Ge _0.85 nanosheet with compressive strain of −2.5% was achieved. Superior gate modulation is evidenced by subthreshold slope of 150 mV/dec and ${I} _{\mathrm{ ON}}/{I} _{\mathrm{ OFF}}>5\times 10^{8}$ ( ${I} _{\mathrm{ OFF}}< 10^{-6}~\mu \text{A}/\mu \text{m}$ and ${I} _{\mathrm{ ON}}>500~\mu \text{A}/\mu \text{m}$ ) measured at $V_{G}= +1V$ , $V_{D} = +1$ V, and $T = 80$ K for our device with channel length of 75 nm.