Experimental Evidence of Sidewall Enhanced Transport Properties of Mesa-Isolated (001) Germanium-On-Insulator pMOSFETs

In this brief, the hole transport properties of narrow-width germanium-on-insulator (GeOI) pMOSFETs are investigated. We report, for the first time, +65% low-field hole mobility enhancement in narrow-width (0.29-mum effective width
W

_eff
) versus large-width (10- mum
W

_eff
) GeOI mesa-isolated devices. The observed enhancement, which is independent of the device length down to 90 nm, is attributed to improved sidewall transport properties resulting in higher hole mobility on the sides than on the top of the devices. At high inversion charge density
N

_inv
~ 10
¹³
cm
^-2
, + 55% hole effective mobility improvement is preserved. The top and side low-field mobilities ( mu
_top
and mu
_side
, respectively) were extracted, showing + 90% mobility improvement at the sides (mu
_top
= 125 cm
²
/V middots
^-1
and mu
_side
= 240 cm
²
/V middots
^-1
).