Ge/Si Heterojunction Tunnel Field-Effect Transistors and Their Post Metallization Annealing Effect

Ge/Si heterojunction tunnel field-effect transistors (TFETs) with an Al₂O₃ gate-stack are demonstrated. The high performances of steep subthreshold swing (SS) of 58 mV/decade and large I_ON/I_OFF ratio over 10⁷ are realized by a proper postmetallization annealing (PMA) process. We can obtain the high-quality Al₂O₃/Ge interface with Dit of as low as ~1011 cm^-2eV^-1 by electron cyclotron resonance oxygen plasma post oxidation. The electrical characteristics of the Ge/SOI TFETs are studied with changing PMA temperature from 200 °C to 400 °C. It is found that Dit between Al₂O₃ and the Si channel region is a critical factor for significantly reducing SS of Ge/Si heterojunction TFETs.