True random number generator based on switching probability of volatile GeXSe1-X ovonic threshold switching selectors

GexSe1-x Ovonic Threshold Switching (OTS) selector is a promising candidate to suppress the sneak current paths in resistive switching memory arrays. A novel method is developed to quantitatively characterize the variations in the threshold voltage (Vth), the hold voltage (Vhd), and the switching probability dependence on the OTS operation conditions. The time-to-switch-on/off (ton/toff) at a constant VOTS follows the Weibull distribution, based on which the dependence of switching probability on pulse waveform, bias, and time can be extracted and extrapolated. Based on this analysis, a novel technique for true random number generator (TRNG) application is proposed. The inherent variability in OTS threshold voltage results in a bimodal distribution of on/off states which can be easily converted into digital bits. The experimental evaluation shows that the proposed TRNG enables the generation of high-quality random bits that passed 12 tests in the NIST statistical test suite without complex external circuits for post-processing.