Silicon-based tunneling field-effect transistor with elevated germanium source formed on (110) silicon substrate

Si-based tunneling field-effect transistors (TFETs) with elevated Ge source were fabricated on Si(110) substrate. The in situ B-doped Ge (Ge:B) source grown on Si(110) has a substitutional B concentration up to 7.8×1020 cm−3, that is more than one order of magnitude higher than that in Ge grown on Si(100) under the same growth conditions. Ge:B epitaxy on (110) and (100) Si is discussed. The TFET with elevated Ge source formed on Si(110) has a subthreshold swing of 85 mV/decade, which is a substantial improvement over that of the control TFET formed on Si(100). This is attributed to the high B doping concentration in the Ge:B(110) source as well as the band gap narrowing effect.