Ambipolar ohmic contact to silicon for high-performance brain-inspired image sensors

Recently, ambipolar semiconductor devices have excelled in developing programmable photodiodes for brain-inspired image sensors, offering energy, speed, and security gains. However, the lack of mature processing techniques makes their manufacture challenging, and the often-adopted Schottky contacts limit their performance. Although CMOS technology is successful in integrated circuits, the employed ohmic contacts can only transport one type of carriers, failing to meet the requirement of electrons and holes working simultaneously in ambipolar devices. Here we propose an ambipolar ohmic contact to Si via a devised complementary ohmic contact configuration (COCC), allowing efficient transport of electrons and holes simultaneously. The process is entirely compatible with CMOS techniques, enabling the manufacture of device arrays at a wafer scale. We demonstrate their application for in-memory sensing and computing image sensors that can process optical images on 2-class MNIST and fashion-MNIST datasets, which can implement recognition tasks within 7.3 ns if possible limitations of peripheral circuits are not considered. The COCC is also applied to manufacture other brain-inspired hardware, including reconfigurable convolution kernels, and synaptic and neuron-like circuits.