Optically addressed ferroelectric memory with nondestructive readout.
We present a review of the emerging optically addressed ferroelectric memory with nondestructive readout as a nonvolatile memory technology, identify its high-impact applications, and project on some novel device designs and architectures that will enable its realization. Based on the high-speed bidirectional polarization-dependent photoresponse, simulation of a readout circuit for a 16-kbit VLSI ferromemory chip yields read-access times of ~20 ns and read-cycle times of ~30 ns (~34 ns and ~44 ns, respectively, within a framework of a radiation-hard environment), easily surpassing those of the conventional electrical destructive readout. Extension of the simulation for a 64-kbit memory shows that the read-access and -cycle times are only marginally increased to ~21 ns and ~31 ns, respectively (~38 ns and ~48 ns, with a radiation-hard readout circuitry). Commercial realization of the optical nondestructive readout, however, would require a reduction in the incident (optical) power by roughly an order of magnitude for the readout or an enhancement in the delivered power-to-size ratio of semiconductor lasers for compact implementation. We present a new two-capacitor memory-cell configuration that provides an enhanced bipolar optoelectronic response from the edges of the capacitor at incident power as low as ~ 2 mW/µm(2). A novel device design based on lead zirconate titanate with the c axis parallel to the substrate is suggested to reduce the requirement of incident optical power further by orders of magnitude.
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Thakoor