Silicon-based partially gated tunnel FETs are characterized under optical and electrical excitation. Most significant outcomes of the experiments are (1) unique characteristics, namely, light induced negative transconductance and optically tunable output resistance (photo-resistor), (2) phototransistor operation that is attained when back-gate is used to store optically generated carriers which in return modulate the transconductance of the transistor in on-state. Simulation results show that the investigated devices have the potential to give rise to new circuit topologies exploiting interaction between light and band-to-band tunneling processes, and improve the area efficiency of pixel sensors owing to their optical gain and charge storage mechanism. (C) 2014 AIP Publishing LLC.