Fast, Energy-Efficient InGaAs Synaptic Phototransistors on Flexible Substrate

Photodetectors sensing the short-wave infrared (SWIR) region have great potential due to their significant advantages in a variety of applications because SWIR light possesses both characteristics of visible light and infrared light. Among them, devices using photodetectors to mimic synaptic dynamics and functions have received a great deal of attention due to their capabilities to implement simplified neural systems. However, it is essential to develop synaptic devices that can operate fast with low energy consumption for more efficient implementation of neural systems. Here, a flexible InGaAs synaptic phototransistor with a fast operation speed of under 1 ms and low energy consumption in the atto joule level is developed to femto joule level which is superior to biological synapses (50 ms, 1–100 fJ). By using InGaAs which has high carrier mobility as a channel layer, weak light, and short optical pulse width, fast operation speed in the SWIR region with low energy consumption is obtained. Moreover, the devices demonstrate synaptic behaviors such as “excitatory post synaptic current”, “paired-pulse facilitation”, “short term plasticity”, “long term plasticity”, and “learning-experience behavior” as neuro-synaptic applications. These results provide the possibilities for implementation of complex synaptic functions with fast speed and low power SWIR synaptic phototransistors.