Highly Stacked 8 $\mathbf{Ge}_{\boldsymbol{0.9}}\mathbf{Sn}_{\boldsymbol{0.1}}$ Nanosheet pFETs with Ultrathin Bodies (~3nm) and Thick Bodies (~30nm) Featuring the Respective Record $\mathbf{I}_{\mathbf{ON}}/\mathbf{I}_{\mathbf{OFF}}$ of 1.4x107 and Record $\mathbf{I}_{\mathbf{ON}}$ of $\boldsymbol{92}\boldsymbol{\mu}\mathbf{A}$ at $\mathbf{V}_{\mathbf{ov}}=\mathbf{V}_{\mathbf{DS}}=$ -0.5V by CVD Epitaxy and Dry Etching

The 8 stacked
${Ge}_{{0.9}}{Sn}_{{0.1}}$
ultrathin bodies with the thickness down to 3nm are realized by the mutual optimization between epitaxy and etching. The 50 epilayers including
${Ge}_{{0.9}}{Sn}_{{0.1}}$
channels,
${Ge}_{{0.97}}{Sn}_{{0.03}}/{Ge}$
caps, Ge:B sacrificial layers, and a Ge buffer by CVD have carefully designed etching characteristics to form uniform ultrathin bodies. The thin double
${Ge}_{{0.97}}{Sn}_{{0.03}}$
caps not only provide sufficient etching selectivity but also stabilize the channel to prevent the bending of the ultrathin bodies. The neutral radicals can isotropically etch the caps and sacrificial layers laterally, and release the 8 stacked ultrathin bodies. Thanks to the quantum confinement (170meV) in the 3nm
${Ge}_{{0.9}}{Sn}_{{0.1}}$
ultrathin bodies, the record
${I}_{{ON}}/{I}_{{OFF}}$
of 1.
$4{x}10^{7}$
at
${V}_{{DS}}={-0.05}{V}$
is achieved among GeSn/Ge 3D pFETs. With the ultrathin bodies, the SS can be reduced to 73mV/dec even with large
${D}_{{it}}{\sim}{10}^{{12}}{cm}^{{-2}}{eV}^{{-1}}$
. For the thick nanosheets (~30nm), the record ION of
${92}{\mu}{A}$
per stack at
${V}_{{OV}}={V}_{{DS}}=-$
0.5V is achieved among all GeSn/Ge 3D pFETs. Thick nanosheets can have higher mobility than ultrathin bodies due to reduced surface roughness scattering and high hole mobility on {110} sidewalls with significant hole population. These 8 stacked channels are the tallest among pFETs.