The origin of massive nonlinearity in Mixed-Ionic-Electronic-Conduction (MIEC)-based Access Devices, as revealed by numerical device simulation

Padilla, Alvaro; Burr, Geoffrey W.; Shenoy, Rohit S.; Raman, Karthik V.; Bethune, Donald S.; Shelby, R. M.; Rettner, Charles; Mohammad, J.; Virwani, Kumar; Narayanan, Pritish; Deb, Arpan Krishna; Pandey, Rajan K.; Bajaj, Mohit; Murali, K. V. R. M.; Kurdi, B. N.; Gopalakrishnan, Kailash

doi:10.1109/drc.2014.6872348

Cited by 3 publications

(6 citation statements)

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“…While copper ions in a healthy symmetric MIEC-based AD are not able to form a filament, these ions do play a critical role in its electrical characteristics. Numerical simulations including both positively-charged copper ions as well as negatively-charged vacancy sites have been able to quantitatively match the electrical characteristics of MIEC-based ADs (figure 5) [6]. These simulations suggest that at low bias, mobile ions settle into a U-shaped distribution with large electric fields at each interface, maintaining a dynamic equilibrium between electrostatic ion drift towards, and ion diffusion away from, each interface.…”

Section: Miecmentioning

confidence: 82%

“…At low bias, Schottky barriers at the MIEC-electrode interfaces are believed to help suppress current flow, leading to the ultra-low leakage. As bias increases in either direction, copper ions and vacancies shift accordingly within the device, modulating the interfaces and leading to an exponential increase in electronic current [6]. Although the current eventually saturates, extremely high current densities have been observed (up to − 50 MA cm 2 (figure 3) [1]).…”

Section: Miecmentioning

confidence: 99%

“…The strong ion accumulation at each interface results in residual electron tunneling at each interface, but strong suppression of holes and hole current. Device turn-ON occurs as hole injection from the positively-biased electrode increases sharply, driven by motion of large populations of copper ions and vacancies [6]. Asymmetry between top and bottom electrodes leads to asymmetric I-V characteristics, since both ion densities and the mapping from current density to current are affected by the geometry of the device with respect to the polarity of operation.…”

Section: Miecmentioning

confidence: 99%

“…These include conventional silicon-based semiconductor devices, oxide semiconductors, threshold switch devices, oxide tunnel barriers, and various approaches for self-selected RRAM [13]. We then review our research on ADs based on mixed-ionicelectronic-conduction (MIEC) [1][2][3][4][5][6][7], and show that these devices are highly suitable for multi-layer crossbar memory for resistive-NVM devices with modest switching voltages. (a) In a crossbar array of resistive-NVM devices, voltage applied at the edge of the array, to select one or more memristor/selectdevice pairs, also affects three other sets of memristor+ADs: those in the same row, in the same column (both half-selected), and all others (un-selected).…”

Section: Introductionmentioning

confidence: 99%

“…Measured I-V characteristics can be matched in simulation, including ultralow leakage currents, voltage turn-ON values, and the > 7 orders of magnitude current increase. Insets show bright-field TEM images of the tested device [6][4]…”

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confidence: 99%

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MIEC (mixed-ionic-electronic-conduction)-based access devices for non-volatile crossbar memory arrays

Shenoy

Burr

Virwani

et al. 2014

Semicond. Sci. Technol.

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Several attractive applications call for the organization of memristive devices (or other resistive non-volatile memory (NVM)) into large, densely-packed crossbar arrays. While resistive-NVM devices frequently possess some degree of inherent nonlinearity (typically 3-30× contrast), the operation of large (> 1000×1000 device) arrays at low power tends to require quite large (> 1e7) ONto OFF ratios (between the currents passed at high and at low voltages). One path to such large nonlinearities is the inclusion of a distinct access device (AD) together with each of the state-bearing resistive-NVM elements. While such an AD need not store data, its list of requirements is almost as challenging as the specifications demanded of the memory device. Several candidate ADs have been proposed, but obtaining high performance without requiring single-crystal silicon and/or the high processing temperatures of the front-end-of-the-linewhich would eliminate any opportunity for 3D stacking-has been difficult. We review our work at IBM Research-Almaden on high-performance ADs based on Cucontaining mixed-ionic-electronic conduction (MIEC) materials [1-7]. These devices require only the low processing temperatures of the back-end-of-the-line, making them highly suitable for implementing multi-layer crossbar arrays. MIEC-based ADs offer large ON/OFF ratios (>1e7), a significant voltage margin V m (over which current <10 nA), and ultra-low leakage (< 10 pA), while also offering the high current densities needed for phase-change memory and the fully bipolar operation needed for high-performance RRAM. Scalability to critical lateral dimensions < 30 nm and thicknesses < 15 nm, tight distributions and 100% yield in large (512 kBit) arrays, long-term stability of the ultra-low leakage states, and sub-50 ns turn-ON times have all been demonstrated. Numerical modeling of these MIEC-based ADs shows that their operation depends on + Cu mediated hole conduction. Circuit simulations reveal that while scaled MIEC devices are suitable for large crossbar arrays of resistive-NVM devices with low (< 1.2 V) switching voltages, stacking two MIEC devices can support large crossbar arrays for switching voltages up to 2.5 V.

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Section: Miecmentioning

confidence: 82%

Section: Miecmentioning

confidence: 99%

Section: Miecmentioning

confidence: 99%