Self-Organized Ge Nanospherical Gate/SiO2/Si0.15Ge0.85–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
_ON
/I
_OFF
> 5 × 10
⁸
(I
_OFF
<; 10
^-6
μA/μm and I
_ON
> 500 μA/μm) measured at V
_G
= +1V , V
_D
= +1 V, and T = 80 K for our device with channel length of 75 nm.