Lee Sunwoo, Jeon Jaeyoung, Eom Kitae, Jeong Chaehwa, Yang Yongsoo, Park Ji-Yong, Eom Chang-Beom, Lee Hyungwoo
Department of Electrical and Computer Engineering, University of Southern California, Los Angeles, CA, 90007, USA.
Department of Physics, Ajou University, Suwon, 16499, Republic of Korea.
Sci Rep. 2022 May 31;12(1):9068. doi: 10.1038/s41598-022-13121-4.
Resistive switching devices have been regarded as a promising candidate of multi-bit memristors for synaptic applications. The key functionality of the memristors is to realize multiple non-volatile conductance states with high precision. However, the variation of device conductance inevitably causes the state-overlap issue, limiting the number of available states. The insufficient number of states and the resultant inaccurate weight quantization are bottlenecks in developing practical memristors. Herein, we demonstrate a resistive switching device based on Pt/LaAlO/SrTiO (Pt/LAO/STO) heterostructures, which is suitable for multi-level memristive applications. By redistributing the surface oxygen vacancies, we precisely control the tunneling of two-dimensional electron gas (2DEG) through the ultrathin LAO barrier, achieving multiple and tunable conductance states (over 27) in a non-volatile way. To further improve the multi-level switching performance, we propose a variance-aware weight quantization (VAQ) method. Our simulation studies verify that the VAQ effectively reduces the state-overlap issue of the resistive switching device. We also find that the VAQ states can better represent the normal-like data distribution and, thus, significantly improve the computing accuracy of the device. Our results provide valuable insight into developing high-precision multi-bit memristors based on complex oxide heterostructures for neuromorphic applications.
电阻开关器件被认为是用于突触应用的多位忆阻器的有前途的候选者。忆阻器的关键功能是高精度地实现多个非易失性电导状态。然而，器件电导的变化不可避免地会导致状态重叠问题，限制了可用状态的数量。状态数量不足以及由此产生的不准确的权重量化是开发实用忆阻器的瓶颈。在此，我们展示了一种基于Pt/LaAlO/SrTiO（Pt/LAO/STO）异质结构的电阻开关器件，它适用于多级忆阻应用。通过重新分布表面氧空位，我们精确控制二维电子气（2DEG）通过超薄LAO势垒的隧穿，以非易失性方式实现多个可调电导状态（超过27个）。为了进一步提高多级开关性能，我们提出了一种方差感知权重量化（VAQ）方法。我们的模拟研究验证了VAQ有效地减少了电阻开关器件的状态重叠问题。我们还发现，VAQ状态可以更好地表示类正态数据分布，从而显著提高器件的计算精度。我们的结果为基于复杂氧化物异质结构开发用于神经形态应用的高精度多位忆阻器提供了有价值的见解。
