Stochastic Computing Based on Volatile Ovonic Threshold Switching Devices

Ovonic Threshold Switching (OTS) selector is essential in the 1S (selector) -1R (resistive switching device) crossbar memory array to suppress the sneak current paths. OTS exhibits inherent stochastic characteristics in its switching process and can be used for implementing true random number generators (TRNGs). Stochastic computing (SC) can be further designed and realized by exploiting the probabilistic switching behavior in the OTS. The stochastic bit streams generated by OTS are demonstrated with good computation accuracy in both multiplication operation and edge detection circuit for image processing. Moreover, the distribution of random bit in the stochastic streams generated by OTS has been statistically studied and linked to the defect de/localization behavior in the chalcogenide material. Weibull distribution of the delay time supports the origin of such probabilistic switching, facilitates further optimization of the operation condition, and lays the foundation for device modelling and circuit design. Considering its other advantages such as simple structure, fast speed, and volatile nature, OTS is a promising material for implementing SC in a wide range of novel applications, such as image processors, neural networks, control systems and reliability analysis.