Current Controlled Relaxation Oscillations in Ge_2Sb_2Te_5-Based Phase Change Memory Devices

The relaxation oscillation of the phase change memory (PCM) devices based on the Ge_2Sb_2Te_5 material is investigated by applying square current pulses. The current pulses with different amplitudes could be accurately given by the independently designed current testing system. The relaxation oscillation across the PCM device could be measured using an oscilloscope. The oscillation duration decreases with time, showing an inner link with the shrinking threshold voltage V_\rm th. However, the relaxation oscillation would not terminate until the remaining voltage V_\rm on reaches the holding voltage V_\rm h. This demonstrates that the relaxation oscillation might be controlled by V_\rm on. The increasing current amplitudes could only quicken the oscillation velocity but not be able to eliminate it, which indicates that the relaxation oscillation might be an inherent behavior for the PCM cell.