Continuous controllable amorphization ratio of nanoscale phase change memory cells

Abstract

The controllable heat behavior, including heat generation and dissipation, is one of the most important physical problems of nanoscale phase-change memory (PCM). A method based on heat accumulation effect to control heat behavior by synthetically modulating the three parameters of applied double pulses is proposed to achieve any expected amorphization ratio. A compact model of nanoscale PCM cells is used to simulate the thermal behavior and amorphization ratio under the condition of single parameter and multi-parameter change of applied double pulses. The results are in good agreement with the experimental results. Repeated experiments also prove the feasibility of continuous controllable amorphization ratio of nanoscale phase-change materials.

Ultralow-power switching via defect engineering in germanium telluride phase-change memory devices

“…5c ) can be used to control the addition and homogenization of defects respectively. It is important to note here that multiple resistance states in PCM reported in earlier works 30 31 32 33 34 were created by controlling the relative volumes of the amorphous and crystalline states, the only two physically different states, and are fundamentally different from the multiple resistance states in this work.…”

“…The recent discoveries of localization effects 35 and defect-templated amorphization 18 in Ge–Sb–Te alloys suggests that defect-engineering approach could be applied to other well-known PCMs too. In addition, with our demonstration of scaling of switching properties in the defect-based approach and multistate switching, we believe that nanoscale PCM structures (mushroom, sidewall, pillar or confined architectures) 5 36 engineered into electronic states in crystalline phase that show localization behaviour in transport will be promising for ultralow-power memories and novel computation strategies 29 30 .…”

“…Progression from state 1 to state 3 by adding more defects either shifts the E F towards the mid-gap, which reduces N ( E F ) and localization length, or creates more paired trap centres, which reduces N ( E F ). Finally, in the amorphous phase, E F is pinned to the mid-gap 30 31 , with N ( E F ) at its minimum value. In the reverse process (SET), by controlled homogenization (removal) of defects from the defect-template region via Joule heating, E F moves back towards the mobility edge, and N ( E F ) starts to increase, accessing all the crystalline intermediate resistance states.…”

Low-loss ultrafast and nonvolatile all-optical switch enabled by all-dielectric phase change materials

“…The phase transition of GST is a thermodynamic process. The crystallization temperature ( T c ) and melting temperature ( T m ) of GST are reported to be 160°C and 600°C ( Terao et al., 2009 )( He et al., 2014 ). To achieve full crystallization especially in a large area, the heating process takes a relatively long time and the temperature has to be kept beyond T c and below T m .…”

Simple square pulses for implementing spike‐timing‐dependent plasticity in phase‐change memory

“…Our previous studies showed that the resistance of PCM can be modulated by voltage pulses with different time intervals based on heat accumulation effect . To estimate the resistance tuning in PCM cell with pre‐ and post‐synaptic spikes, the temperature development is studied.…”