Tunnel field-effect transistors (TFETs) have garnered great interest as an option for the replacement of metal–oxide–semiconductor field-effect transistors owing to their extremely low off-current and fast switching suitable for low-power-consumption applications. However, conventional doped TFETs have the disadvantage of introducing undesirable random dopant fluctuation (RDF) events, which cause a large variance in the threshold voltage and ambipolar leakage current at negative gate voltages. In this study, a simple approach for charge plasma-based doping-less tunnel field-effect transistors (DL-TFETs), including the Ge/Si bilayer frame, which affects the RDF and low on-current issues, was developed by the commercially available Silvaco Atlas device simulator. The use of the Ge/Si bilayer enhances the on-current and point subthreshold swing to 1.4 × 10−6 A and 16.6 mV/dec, respectively. In addition, the dependencies of the Ge/Si junction boundary position and Ge content were examined systematically to attain a firm understanding of the electrical features in DL-TFETs.