A bidirectional threshold switching selector with a symmetric multilayer structure
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. RESEARCH PAPER .
April 2021, Vol. 64 142402:1–142402:6 https://doi.org/10.1007/s11432-020-2960-x
A bidirectional threshold switching selector with a symmetric multilayer structure Qingjiang LI, Kun LI, Yongzhou WANG, Sen LIU & Bing SONG* College of Electronic Science and Technology, National University of Defense Technology, Changsha 410073, China Received 3 May 2020/Revised 3 June 2020/Accepted 18 June 2020/Published online 23 November 2020
Abstract Selectors have been proposed as a highly effective tool for suppressing substantial leakage currents without sacrificing the high density of resistive random-access memory (RRAM) crossbar arrays. Among various selector types, the programmable metallization cell (PMC) selector is promising due to its simple structure and high selectivity. In this work, we demonstrate a new PMC selector that exhibits bidirectional threshold switching behavior by implementing symmetric multilayer dielectrics. The proposed Ag/SiTe/HfO2 /SiTe/Ag selector device has a low off current (< 10−10 A), high selectivity (> 105 ), and low threshold voltage variation (< 0.05). Upon connection to a bipolar RRAM cell via a wire, the proposed selector successfully suppresses the leakage current of an unselected device below the threshold voltage. Keywords threshold switching selector, resistive random access memory, leakage current, programmable metallization cell Citation Li Q J, Li K, Wang Y Z, et al. A bidirectional threshold switching selector with a symmetric multilayer structure. Sci China Inf Sci, 2021, 64(4): 142402, https://doi.org/10.1007/s11432-020-2960-x
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Introduction
The emerging resistive random-access memory (RRAM) is a promising candidate for next-generation non-volatile memory [1–3] and computing devices [4–7]. Nonetheless, the leakage current strongly affects the size and performance of the crossbar array, resulting in increased power consumption [8] and a high probability of operation error [9]. Besides implementing self-rectifying [10] and complementary resistive switching behavior [11] in the RRAM itself, transistors [12], diodes [13], and emerging selectors [14] have been employed as access devices in series with RRAM cells to prevent the generation of a leakage current path. With respect to cell size, bidirectional operation, and fabrication compatibility, selectors are superior to the other options. To date, selectors are primarily based on programmable metallization cells (PMCs) [15, 16], ovonic threshold switching (OTS) [17, 18], and the metal-insulator transition (MIT) [19, 20]. Among these three categories, PMC selectors are promising due to their simple structure and high selectivity. In previous research, we fabricated a PMC selector based on SiTe as a dielectric layer, as this material is amorphous and exhibits a large number ground boundaries, thus facilitating the mobility of Ag ions [21, 22]. The device selectivity and threshold concentration were further optimized by implementing an annealing process [21] and inserting an HfO2 layer [22], respectively. However
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