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The high peak mobility of 509 cm2/ $\text {V}\cdot \text {s}$ of the chemical vapor deposition -grown GeSn pMOSFETs is obtained using 1-nm Ge cap. The Ge cap on GeSn can reduce the scattering of oxide/interface charges and surface roughness for the holes in the GeSn quantum wells. However, the thick cap induces holes in the Ge cap itself, leading lower mobility than GeSn channels. The on current is enhanced by external stress due to the effective mass reduction. The normalized noise power density of the GeSn devices decreases with increasing Ge cap thickness, indicating the carrier number fluctuation and correlated mobility fluctuation are suppressed when the holes are away from interface.

Al electrode on Al2O3/GeOx/Ge dielectrics stack has smaller interface trap density than Pt electrode due to the AlGeO formation at the interface. The AlGeO interfacial layer (IL) is formed during Al deposition. Pt electrode deposition after Al capping/removal process also exhibits the low interface trap density behavior. The increasing Al electrode area decreases interface trap density, indicating the AlGeO passivation is only effective underneath Al electrode. AlGeO layer can effectively passivate Ge with scaled GeOx and Al2O3 thickness. The peak hole mobility in Ge p-MOSFETs with AlGeO IL is 277 cm2/ $\text {V}\cdot \text {s}$ .