A weak electric field-assisted ultrafast electrical switching dynamics in In3SbTe2 phase-change memory devices

Shivendra Kumar Pandey,Anbarasu Manivannan

doi:10.1063/1.4994184

Abstract

Prefixing a weak electric field (incubation) might enhance the crystallization speed via pre-structural ordering and thereby achieving faster programming of phase change memory (PCM) devices. We employed a weak electric field, equivalent to a constant small voltage (that is incubation voltage, Vi of 0.3 V) to the applied voltage pulse, VA (main pulse) for a systematic understanding of voltage-dependent rapid threshold switching characteristics and crystallization (set) process of In3SbTe2 (IST) PCM devices. Our experimental results on incubation-assisted switching elucidate strikingly one order faster threshold switching, with an extremely small delay time, td of 300 ps, as compared with no incubation voltage (Vi = 0 V) for the same VA. Also, the voltage dependent characteristics of incubation-assisted switching dynamics confirm that the initiation of threshold switching occurs at a lower voltage of 0.82 times of VA. Furthermore, we demonstrate an incubation assisted ultrafast set process of IST device for a low VA of 1.7 V (∼18 % lesser compared to without incubation) within a short pulse-width of 1.5 ns (full width half maximum, FWHM). These findings of ultrafast switching, yet low power set process would immensely be helpful towards designing high speed PCM devices with low power operation.

Highlights

This is primarily due to the fact that the set process is essentially governed by a combined effect of both the voltage-dependent ultrafast threshold switching dynamics exemplified by electronic effects,[9,10,11,12] and rapid crystallization of phase change (PC) material induced by Joule heating.[3,13]
The incubation-assisted electrical switching dynamics and set process of several IST cells were characterized in the as-deposited amorphous (∼10 MΩ) phase using the programmable electrical tester (PET) setup
We have demonstrated ultrafast crystallization of IST devices by employing a weak electric field, to the applied voltage pulse, V A. This approach of incubation-assisted switching validates approximately one order faster threshold switching due to thermal prestructural ordering induced by Joule heating, with an extremely small delay time, td of 300 ps, as compared with no incubation voltage (V i = 0 V) for the same V A

Summary

INTRODUCTION

Chalcogenide-based phase change memory (PCM) have substantiated their ability for the generation high-speed, non-volatile memory and towards ‘universal memory’ for future computing systems.[1,2,3,4,5] This is primarily owing to its all-round characteristics such as high read/write speeds, low power consumption, longer endurance, high scalability and non-volatile nature.[6,7] The heart of this memory concept lies in the fascinating property-portfolio of rapid and reversible switching between a high resistivity amorphous (reset) state and a low resistivity crystalline (set) state on a nano/picosecond (ns/ps) timescale triggered by appropriate voltage pulses.[2,3] the overall programming speed of PCM devices is limited by the set process which is slower as compared to the reset process.[8] This is primarily due to the fact that the set process is essentially governed by a combined effect of both the voltage-dependent ultrafast threshold switching dynamics exemplified by electronic effects,[9,10,11,12] and rapid crystallization of phase change (PC) material induced by Joule heating.[3,13] these two factors must be extensively investigated together to improve the speed of set operation Another key factor of a correlation between the speed of set process and thermal stability of amorphous phase (governing data retention) must be discerned to overcome the speed limits of PCM devices.[4,14]. We demonstrate a comparative analysis of switching speed upon systematic increment in V A using the current-voltage characteristics in case of with and without incubation voltage in sub-ns timescale

EXPERIMENTAL DETAILS

RESULTS AND DISCUSSION

CONCLUSION