Ge/Oxide Structured Programmable Phototransistors

A programmable phototransistor built with two Ge/GeO_x/AlO_x:HfO_x/Pd structured RRAM devices is developed. The photon-induced current increase through the Ge/Oxide structured RRAM is explained by the photon-assisted tunneling mechanism when the RRAM is at the low-resistance state. Furthermore, the good output and transfer characteristics, which could be controlled by the light, of the phototransistor are also demonstrated. Since, when both RRAM devices are at the high-resistance state, the structure does not show any optical sensitivity, the phototransistor realized in this letter is programmable. This programmable phototransistor may significantly enhance the performance of photon-electric integrated circuits and reduce the circuit design and fabrication cost.