Breakdown Voltage Enhancement of Nanosheet Transistors by Ultrathin Bodies

A high breakdown voltage of 11.7 V is achieved for a GeSn ultrathin (
$\sim $
2 nm) body nanosheet p-channel field-effect transistor. This voltage is 5.7 V higher than that for a 10-nm GeSn nanosheet. The large effective bandgap associated with the quantum confinement in the
$\sim $
2-nm Ge
$_{{0}.{9}}$
Sn
$_{{0}.{1}}$
channel is responsible for the enhanced breakdown voltage. An extremely scaled Ge
$_{{0}.{9}}$
Sn
$_{{0}.{1}}$
ultrathin body with channel thickness reduced to
$\sim $
2 nm is realized through the co-optimization of low-temperature epitaxy and selective isotropic etching. As-grown Ge
$_{{0}.{9}}$
Sn
$_{{0}.{1}}$
channel layers as thin as 4 nm sandwiched by Ge
$_{{0}.{97}}$
Sn
$_{{0}.{03}}$
/Ge caps are carefully designed for ultrathin bodies. Radical-based highly selective isotropic dry etching is adopted to etch the caps and sacrificial layers and to release the GeSn ultrathin body channels. In addition, owing to strong quantum confinement in the
$\sim $
2-nm ultrathin body, a high
${I}_{\text {ON}}/{I}_{\text {OFF}}$
ratio of
$\ge 1.7 \times 10^{{7}}$
at
${V}_{\text {DS}}$
= -0.5 V is achieved.