GeOI pMOSFETs Scaled Down to 30-nm Gate Length With Record Off-State Current

We present in this letter the most aggressive dimensions reported to date in Ge-channel transistors: pMOSFETs with 30-nm gate length on ultrathin germanium-on-insulator substrates $({T}_{\rm Ge} = \hbox{25}\ \hbox{nm})$. By improving both the Ge-enrichment technique and the transistor fabrication process, we demonstrate devices with controlled threshold voltage $({V}_{\rm th})$ and excellent short-channel effects. Moreover, the low defectivity and the very low thickness of the Ge film lead to a record drain off-state leakage for Ge-channel devices ($<\hbox{1}\ \hbox{nA}/\mu\hbox{m}$ at ${V}_{\rm DS} = -\hbox{1}\ \hbox{V}$) and thus, to the best on-state to off-state current ratio $({I}_{\rm ON}/{I}_{\rm OFF} \sim \hbox{5} \times \hbox{10}^{5})$ , even at ${L}_{g} = \hbox{55}\ \hbox{nm}$.