Strategies for ultra-fast bit generation of two-terminal threshold switch-based true random number generator using drift-free Ge-doped SiO2 threshold switch device

Abstract

To achieve fast random bit generation under 50 ns per bit by employing the threshold voltage (Vth) variation of a simple two-terminal threshold switch (TS) device, we have confirmed that Vth drift-free switching characteristics, along with large Vth variation and fast switching speed, are key factors for implementing true random number generator (TRNG) devices. We analyzed the drift-switching characteristics of various TS devices together with our innovative oxide TS device for TRNG applications. Our findings show that stochastic switching is degraded by the Vth drift characteristics of a conventional ovonic threshold switch (OTS) for fast random bit generation. Conversely, the drift-free insulating-to-metal transition (IMT)-based TS device has very tight Vth variation, which is not suitable as a dynamic entropy source for TRNG. However, the Ge-doped SiO2-based TS device operates with drift-free and large Vth variation switching characteristics. Finally, we successfully demonstrated the potential of a Ge:SiO2-based TS device for TRNG application pertaining to fast random bit generation under 50 ns per bit without a complex circuit system.