Strained GeSn p-Channel Metal–Oxide–Semiconductor Field-Effect Transistors With In Situ Si2H6 Surface Passivation: Impact of Sn Composition

We report a study about the impact of Sn composition on the performance of strained germanium-tin (GeSn) pMOSFETs. GeSn pMOSFETs with Sn compositions of 0.027, 0.040, and 0.075 were fabricated on Ge(001) with an in situ Si
₂
H
₆
passivation. Enhancement in drive current and transconductance is obtained for GeSn pMOSFETs with higher Sn composition due to the smaller capacitance equivalent thickness, the reduced source/drain resistance, and the improved effective hole mobility μeff. Right shift of threshold voltage with Sn composition is observed for the devices. Ge
_0.973
Sn
_0.027
, Ge
_0.960
Sn
_0.040
, and Ge
_0.925
Sn
_0.075
pMOSFETs demonstrate the peak μ
_eff
of 340, 378, and 496 cm
²
/Vs, respectively. At an inversion charge density of 5 × 10
¹²
cm
^-2
, Ge
_0.925
Sn
_0.075
pMOSFETs demonstrate 36% and 24% enhancement in μ
_eff
compared with Ge
_0.973
Sn
_0.027
and Ge
_0.960
Sn
_0.040
devices, respectively. Simulation shows that the enhancement in μeff with Sn composition is resulted from the reduction of hole effective mass and intervalley scattering between heavy and light holes caused by the increased compressive strain.