Received 21 April 2018; revised 5 May 2018; accepted 10 May 2018. Date of publication 15 May 2018;
date of current version 8 June 2018. The review of this paper was arranged by Editor S. Moshkalev.
Digital Object Identifier 10.1109/JEDS.2018.2836400
Threshold Switching Behavior of
Ag-SiTe-Based Selector Device and
Annealing Effect on Its Characteristics
BING SONG , HUI XU, SEN LIU, HAIJUN LIU, AND QINGJIANG LI
College of Electronic Science, National University of Defense Technology, Changsha 410073, China
CORRESPONDING AUTHOR: Q. LI (e-mail: qingjiangli@nudt.edu.cn)
This work was supported in part by the National Natural Science Foundation of China under Grant 61471377, Grant 61704191,
and Grant 61604177, and in part by NUDT Science Support Program under Grant JC-15-04-02.
ABSTRACT Programmable metallization cell is one of important threshold switching selectors. We first
performed a study on the selector based on amorphous chalcogenide material (Si
0.4
Te
0.6
) because of the
rigid structure applied in ovonic threshold s witch. In the meantime, annealing process is implemented
to improve the performance. Results show that devices without annealing process demonstrate a minor
threshold switching characteristic, revealing the potential as selector for cross-point memristor array.
After implementing annealing process, threshold voltage (V
th
), selectivity and endurance of selectors
improve. Meanwhile, requirements of high current and a low holding voltage (V
h
) for an ideal selector
are fulfilled. Using the Ag filament formed during motion of Ag ions, a steep-slope (1.7 mV/dec) for
threshold switching with high selectivity (∼10
4
) could be achieved. Owing to the faster diffusivity of
Ag atoms in solid-electrolytes, the resulting Ag filament easily dissolved under low current regime. It is
deduced that performance improvement is due to the defect reduction within annealing process. Finally,
time characteristics of selector devices are tested to verify fast switching and recovery speed for practical
applicability.
INDEX TERMS Chalcogenide, memristor, programmable metallization cell, resistive random access
memory, Si
0.4
Te
0.6
, threshold switching selector.
I. INTRODUCTION
Memristor is one of the promising candidates for next-
generation nonvolatile memory and neuromorphic computing
applications due to the scalability, 3D stacking potential
and analogy to characteristics of synapse [1]–[3]. In order
to eliminate the sneak path current and reduce the power
consumption in a large crossbar array of memristors, a two-
terminal selector of nonlinear characteristic is introduced
without compromising the scalability and 3D stacking poten-
tial [4], [5]. Among various selectors, threshold switching
selector is more favorable for the low-voltage operation for
their large resistance ratio and high current drive at the ON-
state [6], such as ovonic threshold switch (OTS) [7]–[9],
metal-insulator transition (MIT) [10], [11], field-assisted
superlinear threshold switch (FAST) [12], silicon optoelec-
tronic devices [13], [14] and programmable metallization
cell (PMC) [15]–[17].
Thereinto, programmable metallization cell received
wide attention for their excellent features and sim-
ple structure resembling conductive-bridge random access
memory (CBRAM) [15]–[17]. When the voltage exceeds
threshold voltage (V
th
), the metal filament connects bottom
electrode (BE) and top electrode (TE), switching to high
conductance state called ON-state. In most cases, compli-
ance current is essential for volatile threshold switching to
avert strong filament. In this way, flimsy filament breaks up
after the voltage is removed and devices relax to low conduc-
tance state called OFF state, exhibiting volatile characteristic
rather than nonvolatile memory. Nonetheless, threshold volt-
age of common PMC devices is relatively low and variation
is non-ignorable which is adverse for array application,
according to our previous study which is t he simulation
about the impact of threshold voltage variation on t he array
performance [18].
2168-6734
c
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