Two-dimensional multibit optoelectronic memory with broadband spectrum distinction

Abstract

Optoelectronic memory plays a vital role in modern semiconductor industry. The fast emerging requirements for device miniaturization and structural flexibility have diverted research interest to two-dimensional thin layered materials. Here, we report a multibit nonvolatile optoelectronic memory based on a heterostructure of monolayer tungsten diselenide and few-layer hexagonal boron nitride. The tungsten diselenide/boron nitride memory exhibits a memory switching ratio approximately 1.1 × 106, which ensures over 128 (7 bit) distinct storage states. The memory demonstrates robustness with retention time over 4.5 × 104 s. Moreover, the ability of broadband spectrum distinction enables its application in filter-free color image sensor. This concept is further validated through the realization of integrated tungsten diselenide/boron nitride pixel matrix which captured a specific image recording the three primary colors (red, green, and blue). The heterostructure architecture is also applicable to other two-dimensional materials, which is confirmed by the realization of black phosphorus/boron nitride optoelectronic memory.

Two‐Terminal Multibit Optical Memory via van der Waals Heterostructure

“…Each cycle includes 1) programming, 2) off-current reading, 3) erasing, and 4) on-current reading processes. [14,[28][29][30][31] Under this V DS-pro pulse bias, the I DS abruptly increased to ≈10 −3 A ((1) in Figure 1c). Owing to the intrinsically n-doped MoS 2 (see Section S5, Supporting Information), the channel exhibited reasonably high conductance, I DS ≈ 5 × 10 −10 A with V DS-read = 0.5 V in the dark.…”

“…Accordingly, the initial current ratio decreases 2000 times to ≈500 after 3.6 × 10 4 s. The long retention time of our device can be ascribed to the large electron barrier of MoS 2 /h-BN (≈2.7 eV), [9] which suppresses electron tunneling between the MoS 2 channel and floating graphene. [30,36] We further investigated the pulse power-dependent photoresponse memory at 458 nm with a fixed exposure time of 1 s, as shown in Figure 3b (638 nm in Figure S6a, Supporting Information). Each P/E cycle includes programming by a negative V DS-pro pulse (−12 V, 0.2 s), off-current reading for 0.5 s, erasing by a 458 nm light pulse (400 nW, 0.4 s), and on-current reading for 0.5 s. The current was measured at V DS = 0.5 V. The largely unchanged on-and off-current after 10 4 P/E cycles indicates the high durability and stability of the MoS 2 /h-BN/graphene memory.…”

“…Figure 2b shows the off-and on-current of 10 4 P/E cycles with an interval of 100 cycles. [30] Figure 3c shows the variation of the on-state I DS as a function of pulse power-P at 458 nm in semi-log (left axis) and linear (right axis) scales. This reliability of the device is attributed to its extreme stability against voltage stress imparted by the h-BN dielectric layer.…”

“…[5,28] This results in short retention times and sensitivity to environmental factors. [30] Despite the long retention time and high on/off ratios of the recently developed vdWs heterostructure-based optical memory 2D van der Waals (vdWs) heterostructures exhibit intriguing optoelectronic properties in photodetectors, solar cells, and light-emitting diodes. [29] Similarly, by storing charge in the hexagonal boron nitride (h-BN) dielectric layer, the WSe 2 /h-BN-FET-based optical memory on silicon also exhibited a high on/off ratio of 1.1 × 10 6 , realizing a data storage capability of up to 128 distinct states.…”

Recent Advances in Memory Devices with Hybrid Materials

“…Moreover, mixed phase (2H and 1T) hybrid materials which possess semiconducting and metallic region, the Al/1T@2H-MoS 2 -PVP/ITO/PET showed WORM memory effect due to the internal electric field which protects the trapped electrons from being detrapped. [118] Controlling the polarity of the backgate enabled the programming and erasing process under light illumination. [25,[112][113][114] The memory performance of MoS 2 composite-based ReRAM is summarized ( Table 2).…”