Redefining the Speed Limit of Phase Change Memory Revealed by Time-resolved Steep Threshold-Switching Dynamics of AgInSbTe Devices

Abstract

Although phase-change memory (PCM) offers promising features for a ‘universal memory’ owing to high-speed and non-volatility, achieving fast electrical switching remains a key challenge. In this work, a correlation between the rate of applied voltage and the dynamics of threshold-switching is investigated at picosecond-timescale. A distinct characteristic feature of enabling a rapid threshold-switching at a critical voltage known as the threshold voltage as validated by an instantaneous response of steep current rise from an amorphous off to on state is achieved within 250 picoseconds and this is followed by a slower current rise leading to crystallization. Also, we demonstrate that the extraordinary nature of threshold-switching dynamics in AgInSbTe cells is independent to the rate of applied voltage unlike other chalcogenide-based phase change materials exhibiting the voltage dependent transient switching characteristics. Furthermore, numerical solutions of time-dependent conduction process validate the experimental results, which reveal the electronic nature of threshold-switching. These findings of steep threshold-switching of ‘sub-50 ps delay time’, opens up a new way for achieving high-speed non-volatile memory for mainstream computing.

A scheme for enabling the ultimate speed of threshold switching in phase change memory devices

“…They exploit the unique feature of TS as a rapid breakdown of electrical resistance at V T . This is observed after a finite delay time ( t d ) measured as the time between voltage exceeding the threshold value V T (onset) and a steep rise in the device current (end) 6 , 12 , 19 . TS dynamics of various PCM devices show a strong voltage dependence on t d 16 , 18 , 20 , 21 .…”

“…Therefore, the major challenge lies in achieving electrical switching in GST devices below 10 ns, which forms the primary goal of this paper. Threshold switching has been studied in both melt-quenched and as-deposited amorphous phases 18,19 . However, melt-quenching process is known to leave some subcritical crystalline domains in the amorphous matrix, so that the slow nucleation step is bypassed during the switching process 25 .…”

Direct Evidence for a Systematic Evolution of Optical Band Gap and Local Disorder in Ag, In Doped Sb2Te Phase Change Material

“…Introduction : Chalcogenide‐based phase change (PC) materials undergo rapid and reversible switching from high‐resistance amorphous (binary “0”) to low‐resistance crystalline (binary “1”) phase, accompanied by large property contrast in terms of resistivity and/or reflectivity and is exploited in data storage and plasmonic device applications . Recent studies on Ag, In doped Sb 2 Te (AIST) material has demonstrated ultrafast electrical switching and crystallization dynamics in picosecond timescale . This makes it as a strong contender for the next generation ultrafast non‐volatile memory technology.…”

Exploring ultrafast threshold switching in In3SbTe2 phase change memory devices

“…Time-resolved current-voltage characteristics and threshold switching dynamics of IST device have been extensively studied using an advanced Programmable Electrical Test (PET) system, specially designed for investigating ultrafast switching dynamics of memory devices at the ps-timescale 16,29 . A schematic diagram of the experimental setup is shown in Fig.…”

“…Subsequently, Joule heating causes an abrupt increase in device current, I d leading to the formation of the set state 20 . Threshold switching is known to occur after a finite delay time, t d 18,21 measured as the time duration between the device experiencing V T and a sharp rise in I d 16,22 . t d is an important parameter that depends on the amplitude of the applied voltage pulse, V A .…”