Modeling the Current–Voltage Characteristics of Ge₁₋ₓSnₓ Electron–Hole Bilayer TFET With Various Compositions

In this article, we present, for the first time, the results of simulation and analysis of the current-voltage characteristics of germanium-tin electron-hole bilayer tunnel field-effect transistor (EHB TFET) of various compositions of the semiconductor substrate. Ge
_1-x
Sn
_x
is an interesting material due to the possibility of tuning the band structure by changing the Sn content. The direct and indirect bandgap of GeSn can be changed to affect the direct and phonon-assisted band-to-band tunneling currents. In this article, both currents are calculated for various compositions of Ge
_1-x
Sn
_x
and the channel body thickness as a parameter. The simulated structure exhibits steep-slope current-voltage characteristics due to the reduced carrier dimensionality and the use of 2-D-2-D tunneling as the transport mechanism. Sudden current bumps on characteristics are related to the alignment of the subsequent hole and electron energy levels in the gate-induced surface quantum wells. An increase in the Sn content results in a boost of the ON-current, which is related to the higher magnitude of the direct tunneling current. This effect depends strongly on the body thickness. We show that the application of GeSn in EHB TFET structure can be beneficial in terms of low-power applications.