Impact of Asymmetric Configurations on the Heterogate Germanium Electron–Hole Bilayer Tunnel FET Including Quantum Confinement

We investigate the effect of asymmetric configurations on the heterogate germanium electron-hole bilayer tunnel FET (TFET) and assess the improvement that they provide in terms of boosting the typically very low ON-current levels of TFET devices in the presence of field-induced quantum confinement. We show that when a very strong inversion for holes is induced at the bottom of the channel, the formation of the inversion layer for electrons is shifted to higher gate voltages, which in turn enhances the electrostatic control of the band bending at the top of the channel. As a result, the pinning of the quantized energy subbands is prevented for a wider range of gate voltages, and this allows vertical band-to-band tunneling distances to be further reduced compared with the conventional symmetric electron-hole bilayer configurations.