Germanium–Tin (GeSn) p-Channel MOSFETs Fabricated on (100) and (111) Surface Orientations With Sub-400 <formula formulatype="inline"><tex Notation="TeX">$^{\circ}\hbox{C}\ \hbox{Si}_{2}\hbox{H}_{6}$</tex> </formula> Passivation

In this letter, we report the first study of the dependence of carrier mobility and drive current I <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Dsat</sub> of Ge <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.958</sub> Sn <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.042</sub> p-channel metal-oxide-semiconductor field-effect transistors (pMOSFETs) on surface orientations. Compressively strained Ge <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.958</sub> Sn <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.042</sub> channels were grown on (100) and (111) Ge substrates. Sub-400°C Si <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">6</sub> 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 IDsat over the (100)oriented one at a V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">GS</sub> -V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">TH</sub> of -0.6 V and V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">DS</sub> 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.