Principle of photoconductive ferroelectric memory and preliminary experiments

A novel concept called photoconductive ferroelectric memory (PFM) is propos ed as a means to fabricate ferroelectric random access memories (FeRAMs). T he memory device is based on the new operating principle that skillfully in tegrates the photoconductive effect of the semiconductor with the spontaneo us polarization reversal and the pyroelectric effect of ferroelectrics. The entire multilayer structure of the device consists of indium-(in oxide OTO )/a-Si:H/lead zirconate titanate (PZT)/bottom electrode. The operating prin ciple of the PFM device is designed and theoretically calculated, and the d evice is then prepared by RF magnetron sputtering. The photoconductive effe ct of amorphous silicon due to the focused laser light is used for address. The remanent polarization directions of the PZT layer are used for "1" or "0" of memory. The pyroelectric current directions are used for readout. Th e write-read operation of PFM is proven by observing the hysteresis loop in a single cell and different pyroelectric current direction readouts by lig ht beam illumination.