Highly Uniform Resistive Switching Performances Using Two-Dimensional Electron Gas at a Thin-Film Heterostructure for Conductive Bridge Random Access Memory

Abstract

This research demonstrates, for the first time, the development of highly uniform resistive switching devices with self-compliance current for conductive bridge random access memory using two-dimensional electron gas (2DEG) at the interface of an Al2O3/TiO2 thin-film heterostructure via atomic layer deposition (ALD). The cell is composed of Cu/Ti/Al2O3/TiO2, where Cu/Ti and Al2O3 overlayers are used as the active/buffer metals and solid electrolyte, respectively, and the 2DEG at the interface of Al2O3/TiO2 heterostructure, grown by the ALD process, is adopted as a bottom electrode. The Cu/Ti/Al2O3/TiO2 device shows reliable resistive switching characteristics with excellent uniformity under a repetitive voltage sweep (direct current sweep). Furthermore, it exhibits a cycle endurance over 107 cycles under short pulse switching. Remarkably, a reliable operation of multilevel data writing is realized up to 107 cycles. The data retention time is longer than 106 s at 85 °C. The uniform resistance switching characteristics are achieved via the formation of small (∼a few nm width) Cu filament with a short tunnel gap (<0.5 nm) owing to the 2DEG at the Al2O3/TiO2 interface. The performance and operation scheme of this device may be appropriate in neuromorphic applications.

Oxide-Electrolyte Thickness Dependence Diode-Like Threshold Switching and High on/off Ratio Characteristics by Using Al2O3 Based CBRAM

“…The extremely high on/off ratio is promising for multilevel switching [31,32] and future neuromorphic computing to ensure the enhance conduction states. Though the device is unable to go for long P/E endurance keeping such a high order on/off ratio, still this result is comparable with recently published works as listed in Table 1 [10,11,[33][34][35][36][37][38]. By reducing pulse width from 500 µs to 1 µs, P/E cycles are improved to 100 P/E cycles, as shown in Figure 7b.…”

“…After formation of the pristine devices, a reduction and oxidation at the neck region will be responsible for LRS and HRS of the devices. For the S2 devices, the high electric filed controls across [11] 7/−9 0.1/10 5/5 10 7 10 5 10 6 Cu/TaO x /Ta 2 O 5-x /Pt [33] -/-0.1/0.1 -3000~10 5 >10 4 at 85 • C Cu/HfO 2 :Cu/Pt [34] -/-1/1 0.01/100 >100 10 7 10 5 Al/CH 3 NH 3 Pbl 3 :PVA m.Hl/ITO/Glass [35] 3/−1 100/100 10 4 /10 4 500 >10 5 10 4 Cu/Ti/PVP-PMF/Pt [36] 1/−0.5 1/5 10 4 /10 4 >10 3 >10 3 >10 3 at 85 • C Ag/HfO x :N/Pt [37] 2/-0.1/-50/50 10 6 5 × 10 8 -Cu/NG/HfO 2 [38] 4/−4 0.5/0.5 0.5/0.5 10 7 >10 6 2 × 10 5 at 125 • C…”

Harnessing Conductive Oxide Interfaces for Resistive Random-Access Memories

“…These oxide interfaces provided a fertile ground for the discovery and manipulation of extraordinary physics, such as superconductivity [2][3][4][5], magnetism [6,7], magnetoelectric coupling [8,9], Rashba spinorbit coupling [10], persistent photoconductivity [11,12], and integer/fractional quantum Hall effect [13,14]. Over the last decade, leveraging these phenomena towards various devices, such as transistors [15][16][17][18][19], diodes [20], gas sensors [21], spintronic devices [22,23], and memory devices [24][25][26][27][28][29], has drawn considerable attention. In addition to the exotic phenomena listed above, the emergence of a high sheet density of electrons (typically 10 12 ∼10 15 cm −2 ) between two insulators is already attractive for some devices, such as in the role of channels or back electrodes.…”

“…Among their various device prospects, recently, 2DEGs were utilized for resistive random-access memories (RRAMs) [24][25][26][27][28]. RRAM devices [34][35][36] are highly attractive for the nextgeneration memories [37,38] and new computing paradigms [39][40][41][42][43][44][45][46].…”

“…The use of amorphous oxide on single crystal oxide substrates [16,24,30,31,[64][65][66][67][68] (Figure 1B) lowered the oxide deposition temperatures to <300 °C and expanded the deposition methods to ALD. The use of amorphous oxides deposited on polycrystalline oxide [17,21,25,32,33,69], which we term "All-ALD 2DEGs", provides a great advantage towards scalability and integration with existing and future technologies (Figure 1C). We note that significant progress has been demonstrated in MBE-based integration of epitaxial oxide 2DEGs systems with silicon [70][71][72] and other semiconductors [73,74].…”