Resistance drift in Ge2Sb2Te5 phase change memory line cells at low temperatures and its response to photoexcitation

Resistance drift in amorphous Ge2Sb2Te5 is experimentally characterized in melt-quenched line cells in the range of 300K to 125K and is observed to follow the previously reported power-law behavior with drift coefficients in the range of 0.07 to 0.11 in the dark, linearly decreasing with 1/kT. While these drift coefficients measured in the dark are similar to commonly observed drift coefficients (similar to 0.1) at and above room temperature, measurements under light show a significantly lower drift coefficient (0.05 under illumination vs 0.09 in the dark at 150K). Periodic on/off switching of light shows a sudden decrease/increase in resistance, attributed to photo-excited carriers, followed by a very slow response (similar to 30min at 150K) attributed to contribution of electron traps and slow trap-to-trap charge exchanges. A device-level electronic model is used to relate these experimental findings to gradual charging of electron traps in amorphous Ge2Sb2Te5, which gives rise to growth of a potential barrier for holes in time and, hence, resistance drift. Published under license by AIP Publishing.