Fabrication and characterization of 3D stackable broadband photoresponsive InGaAs biristor neuron for neuromorphic visual system

Abstract

In this study, broadband photoresponsivity of single transistor latch characteristics of an InGaAs biristor neuron for a neuromorphic visual system is shown. Electrical characteristics and photoresponsivity are measured on the vertical mesa of an epitaxially-grown N+InGaAs/P-InGaAs/N+InGaAs wafer. When a proper current bias is applied on a biristor, it makes a spiking voltage signal with a corresponding value. A photoresponsive InGaAs biristor neuron suitable for neuromorphic visual systems is demonstrated. It receives optical signals, converts them to electrical signals, and simultaneously transmits spiking signals to a neural network. This feature is attractive for an input neuron in spiking neural networks (SNNs). A visible and infrared (IR) light photoresponse with near 1 V operation was achieved thanks to the narrow bandgap energy of the InGaAs. This permits broadband detection with lower energy consumption and higher speed compared to previous Si-based neurons. Furthermore, monolithic 3D integration (M3D) of photoresponsive neurons over the synapses is available to construct a 3D neuromorphic visual system, which also minimizes the interconnect bottleneck because of its inherently low temperature fabrication.