Despite rapid progress, conventional floating-gate nonvolatile memory devices still face critical challenges. Optoelectronic memory devices (OEMs) based on two-dimensional (2D) van der Waal heterostructures (vdWhs) are a promising solution but suffer from reliability and endurance issues. Addressing these shortcomings, researchers have developed a novel rhenium selenide and 2D tellurene-based vdWh with multilevel storage capabilities, marking a significant step in OEM development.
Floating-gate (FG) nonvolatile memory technology has witnessed rapid development in recent years, offering several advantages in areas like the Internet of Things, multilevel data storage, and next-generation flash memory. Despite this progress, critical challenges such as reducing memory cell size and power consumption are still not solved.
A promising solution to these challenges lies in optoelectronic memory (OEM) devices, which can convert light to electricity and vice versa, based on two-dimensional (2D) van der Waal heterostructures (vdWhs). These heterostructures are composed of 2D material layers stacked in a precise order with weak inter-layer bonds, endowing them with unique optoelectrical properties. Previous studies have explored vdWh OEMs using different materials, including graphene, black phosphorous, and perovskite. However, these devices suffer from narrow light absorption spectrums, low on-off switching ratios, and low data retention, limiting their long-term use and reliability.
To address these problems, a team of researchers from Dongguk University, Korea, led by Professor Hyunsik Im from the Division of Physics and Semiconductor Science, has developed a novel high-performance OEM based on rhenium disulfide (ReS2)/hexagonal boron nitride (hBN)/tellurene (2D Te) vdWh. Their findings were made available online on January 11, 2024, and published in Volume 18, Issue 05 of the journal ACS Nano on February 06, 2024.
The researchers fabricated the OEM device by stacking a few layers of ReS2 on top of a hBN layer followed by a 2D Te FG, all on a silicon dioxide substrate. Tests revealed that the ReS2/hBN/2D Te vdWh device exhibits exceptional long-term stability, a high on/off switching ratio of the order of 106, and impressive data retention, owing to the excellent optoelectrical properties of ReS2 and 2D Te. Moreover, it also demonstrated a broad absorption spectrum extending from the visible to near-infrared region at room temperature.
Expanding on the results, Prof. Im says, “Our device can achieve multi-bit storage states by varying the gate voltage, input laser wavelength and laser power, enabling complex data patterns and high data capacities.” Furthermore, the device can perform fundamental OR and AND Boolean logic gate operations, crucial for digital circuits, by combining electrical and optical inputs.
“Our research marks a significant milestone in multi-bit optoelectronic memory technology, holding great potential in various applications, including artificial intelligence systems, cloud computing, and broadband optical programmability for digital circuits,” concludes Prof. Im.
