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In this work, the nonlinear (NL) characteristics of bi-layer high-k/low-k dielectrics structure, i.e. high-k layer with the low-k layer, are for selectorless oxide-based resistive random-access memories (RRAM) memory array application. It has been shown that such structure enhances the read currents at full read voltage (∼10-3 A) as compared to the bi-layer low-k/low-k structure (∼10-4 A), reduces low-voltage current, increases I-V nonlinearity and thereby suppresses the sneak path currents in the selectorless RRAM. Improved seasoning effect has also been demonstrated using the bilayer dielectric structure. The Fowler-Nordheim tunneling behavior has been found in the first RESET process (-0.45 to -1.25 V) as followed by the high self-rectifying characteristics that enlarge the immunity to the sneak path current and reduce the read errors in the array applications. The breakdown controllability of the forming process dominates the followed seasoning cycles which leads to two different performances in bilayer stacks i.e. efficient seasoning and inefficient seasoning, which provides an intrinsic design of selectorless RRAM devices. The device characteristics with current transport mechanisms have also been investigated. Our results provide additional insights into ways to achieve high performance and excellent reliability of built-in nonlinearity in selectorless RRAM (NL > 120, memory window > 100, sub-μs switching speed, and NL retention) for the future low-power RRAM memory array configurations.

We have grown high-quality InxGa1-xN/GaN triple-quantum-well microdisks on LiAlO2 substrate by plasma-assisted molecular beam epitaxy. The InxGa1-xN/GaN microdisk with a hexagonal shape of oblique face 28o-angle off c-axis was achieved. The mechanism of the termination of awl-shaped growth and the growth rates of GaN-barrier and InxGa1-xN-well were evaluated and confirmed with the triple quantum wells. Based on the growth rates and 28o-angle geometric shape, one can control the finite size of InGaN/GaN microdisks by plasma-assisted molecular beam epitaxy.

InN hexagonal thin wurtzite disks were grown on γ-LiAlO2 by plasma-assisted molecular-beam epitaxy at low temperature (470oC). The ( 000 1 ¯ ) InN thin disk was established with the capture of N atoms by the β ¯ -dangling bonds of most-outside In atoms, and then the lateral over-growth of the In atoms were caught by the β ¯ -dangling bonds of the N atoms. From the analyses of high-resolution transmission electron microscopy, the lateral over-grown width was extended to three unit cells at [ 1 1 ¯ 00 ]InN direction for a unit step-layer, resulting in an oblique surface with 73o off c-axis.