A novel non-volatile optoelectronic memory: the Photon-Triggered FGMOS

A novel non-volatile opto-electronic memory at a wavelength of 850 nm is presented. The memorization principle exploits the same concept of floating-gate metal-oxide-semiconductor (FGMOS) memories, i.e. the trapping of charges in a floating gate. The basic memory cell of the Photon-Triggered FGMOS (PTFGMOS) is realized through the physical combination of a FGMOS and a silicon waveguided structure; each photon absorbed by silicon, generates an electron-hole pair. The high voltage applied to the control gate of the FGMOS attracts the generated free electrons towards the floating gate, trapping them (tunnel effect) even after the control gate voltage is lowered. Hence, the electrons trapped in the floating gate affect the threshold voltage of the MOSFET, thus making the memory easily readable electrically. The device provides a useful way to directly store the information from the optical to the electrical domain. The footprint of the designed PTFGMOS single cell is 5 μm × 2 μm.