Electrical switching in chalcogenide liquid semiconductors

Reversible electrical switching from a higher resistance off-state to a lower resistance on-state has been observed in several chalcogenide semiconductor alloys both in the solid and liquid phases. Experiments conducted between 100 and 500°C showed that the threshold switching voltage decreases with increasing ambient temperature, and that the on-state resistance remains relatively constant up to the melting region but generally increases thereafter. The alloy Se_0.77Te_0.13S_0.10 shows a preserved on-state which can be maintained using 60 Hz ac in both the solid and liquid phases. The on-state can be reversed to the off-state by decreasing the applied field, and hence is not a conventional memory state. Below the melting region (250°C) the on-state I–V curve has a distinct knee or barrier voltage above which the current increases steeply. Above the melting range the knee becomes less clearly defined and occurs at a lower voltage. Below 345°C the above alloy has an activation energy of 0.37 eV. At this temperature an abrupt slope change or a discontuinity exists in the temperature dependence of off-state resistance, threshold field, threshold power and on-state resistance.