Evidence of Avalanche Multiplication in GeSeAs Ovonic Threshold Switch Selectors

The switching characteristics for Ge10Se54As36 (GSA) ovonic threshold switch (OTS) selectors as a function of the OTS thickness were examined for various devices. We find that thicker GSA devices (20 and 30 nm) switch at lower effective electric fields compared to the 10 nm GSA device. In addition, the OFF state I–V curves for thicker GSA devices exhibit different functional regimes, indicating the presence of additional transport mechanisms. To explain this thickness dependence, we expand the lucky drift electron model for avalanche multiplication so that it can handle nanoscale thin films. Using this model, we show that avalanche multiplication is enhanced in thicker GSA OTS devices and this can explain the observed thickness dependence. This work provides unambiguous experimental evidence that avalanche breakdown plays a role in OTS switching.