High gain hot-carrier WSe2 phototransistor with gate-tunable responsivity

Abstract

Hot-carrier injection at semiconductor/metal interface shows great potentials in infrared photodetection. However, the photoresponsivity of hot-carrier photodetector with diode mode is still limited in the scale of 1 mA/W due to the low injection efficiency of hot carriers and the lack of gain. Here, we demonstrate a high gain hot-carrier WSe₂ phototransistor with gate-tunable responsivity. In this device, plasmonic resonances is used to enhance the light absorption of gold nanodisk, which provide hot holes. The hot holes are trapped into WSe₂ and recycled in WSe₂ channel in lateral direction, which introduce high gain for photodetection. Experiment shows that the photoresponsivity of the device can be over 0.23 A/W with a gain of 270 at the wavelength of 1310 nm. More interestingly, the responsivity of the device can be tuned by gate, which can be used to encode synaptic weights of the sensor pixel.