Resistance drift in phase change materials is characterized in amorphous phase change memory line-cells from 300 K to 125 K range and is observed to follow the previously reported power-law behavior with drift coefficients in the 0.07 to 0.11 range in dark. While these drift coefficients measured in dark are similar to commonly observed drift coefficients (~0.1) at and above room temperature, measurements under light show a significantly lower drift coefficient (0.05 under illumination versus 0.09 in dark at 150K). Periodic on/off switching of light shows sudden decrease/increase of resistance, attributed to photo-excited carriers, followed by a very slow response (~30 minutes at 150 K) attributed to contribution of charge traps. Continuation of the resistance drift at low temperatures and the observed photo-response suggest that resistance drift in amorphous phase change materials is predominantly an electronic process.
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