The influence of network rigidity on the electrical switching behaviour of Ge-Te-Siglasses suitable for phase change memory applications

Ge15Te85-xSix (2 <= x <= 12) glasses of a wide range of compositions have been found to exhibit electrical switching at threshold voltages in the range 100 - 600V, for a sample thickness of 0.3 mm. The samples become latched to the ON state (memory behaviour) at higher ON state currents (> 1 mA). However, the switching is found to be reversible ( threshold behaviour) if the ON state current is limited to lower values (<= 0.7 mA). While Ge15Te85 (-) Si-x(x) glasses with x <= 5 exhibit a normal electrical switching, an unstable behaviour is seen in the I - V characteristics of Ge15Te85 (-) Si-x(x) glasses with x > 5 during the transition to the ON state. Further, a sparking in the electrode region and the splashing of the active material is observed in Ge15Te85 Si-- x(x) glasses with x > 5. It is also interesting to note that the switching voltage (V-T) and initial resistance (R) of Ge15Te85 (-) Si-x(x) glasses increase with addition of Si, exhibiting a change in slope at a composition x = 5 (< r >=2.4). The observed electrical switching behaviour of Ge15Te85 Si-- x(x) glasses has been understood on the basis that the composition x = 5 is the rigidity percolation threshold of the Ge15Te85 (-) Si-x(x) system. It is also proposed that the Ge15Te85 (-) Si-x(x) glasses with x < 5 are likely to be more suitable for phase change memory applications.