Germanium–Tin (GeSn) p-Channel MOSFETs Fabricated on (100) and (111) Surface Orientations With Sub-400 $^{circ}hbox{C} hbox{Si}_{2}hbox{H}_{6}$ Passivation

摘要

In this letter, we report the first study of the dependence of carrier mobility and drive current $I_{rm Dsat}$ of $ hbox{Ge}_{0.958}hbox{Sn}_{0.042}$ p-channel metal–oxide–semiconductor field-effect transistors (pMOSFETs) on surface orientations. Compressively strained $ hbox{Ge}_{0.958}hbox{Sn}_{0.042}$ channels were grown on (100) and (111) Ge substrates. Sub-400 $^{circ}hbox{C} hbox{Si}_{2}hbox{H}_{6}$ treatment was introduced for the passivation of the GeSn surface prior to gate stack formation. Source/drain series resistance and subthreshold swing $S$ were found to be independent of surface orientation. The smallest reported $S$ of 130 mV/decade for GeSn pMOSFETs is achieved. The (111)-oriented device demonstrates 13% higher $I_{rm Dsat}$ over the (100)-oriented one at a $V_{rm GS}$ –$V_{rm TH}$ of $-$0.6 V and $V_{rm DS}$ of $-$0.9 V. We also found that GeSn pMOSFETs with (111) surface orientation show 18% higher hole mobility than GeSn pMOSFETs with (100) orientation.