Electronic and Optoelectronic Devices based on Two‐Dimensional Materials: From Fabrication to Application

Abstract

promising and important 2D material. Graphene-based electronic and optoelectronic device applications [11][12][13][14][15] have been widely researched to take advantage of its many outstanding properties, such as high carrier mobility (10 000 cm 2 V −1 s −1 at room temperature), [16] excellent optical transparency (97% for monolayer), [17] high Young's modulus (0.5-1 TPa), [18] and wide absorption spectrum (300-1400 nm). [19] The unique properties of graphene have also triggered extensive research in other 2D materials including TMDs, particularly for various electronic [4,[11][12][13] and optoelectronic device applications. [3,5,14,15,24,31, 2D electronic devices have advanced from single junction to heterojunction devices and have recently been used in lateral/vertical field-effect transistors (FETs), [4,[11][12][13][62][63][64]67,68] negative differential resistance (NDR) devices, [42][43][44][45][46][47][48][49][50]66] and memory devices. [51][52][53][54][55][56][57][58][59][60][61]65] Especially, type-II heterojunctions have enabled efficient electron-hole separation during the conversion from light to current, and these have found use in high-performance 2D optoelectronic devices such as photodetectors, [3,5,14,15,24,31,[69][70][71][72][73][74][75][76][77][78][79][80][81][82][83]102,103] photovoltaic devices, [84][85][86][87][88][89][90][91][92][93][94][95] and light-emitting diodes (LEDs). [87,88,[95][96][97][98][99][100][101] The electronic and optoelectronic properties of semiconducting TMDs depend on the number of layers due to quantum confinement effects. [104,105] For example, the transition from an indirect energy bandgap to a direct bandgap was observed for molybdenum-and tungstenbased TMDs as layer thickness decreases and approaches a monolayer. It has been reported that bulk molybdenum disulfide (MoS 2 ) and tungsten diselenide (WSe 2 ) have an indirect bandgap of 1.2 eV, whereas monolayer MoS 2 and WSe 2 have direct bandgaps of 1.88 eV and 1.65 eV, respectively, which lead to a high on/off-current ratio and high quantum efficiency. [106] Meanwhile, rhenium disulfide (ReS 2 ) exhibited a direct bandgap of 1.44 eV independent of its layer thickness, [107] and it is considered a promising candidate for future optoelectronic devices. [24,31,33,82,83] In this review, we first introduce important fabrication techniques of i) doping, ii) contact engineering, and iii) heterojunction formation for improving the performance of 2D-material-based devices in terms of fieldeffect mobility, on-current, responsivity, and temporal response (Section 2). We then discuss promising 2D-material-based electronic (Section 3) and optoelectronic (Section 4) devices,Since the rediscovery of graphene in 2004, this material has attracted an enormous amount of interest owing to its unique structural, mechanical, electronic, and optical properties. Beyond this, the unique properties of graphene have also triggered extensive research on other two-dimensional (2D) materials including transition metal dichalcogenides (TMDs), part...

Emerging in‐plane anisotropic two‐dimensional materials

“…Although many works have reported the device applications of FETs and photodetectors based on these low‐symmetrical 2D materials, they do not stress the in‐plane anisotropic properties. In fact, the recent progress of electronic and optoelectronic applications based on 2D materials have been well reviewed . Here, we only review the device applications based on the utilization of intrinsic in‐plane anisotropic properties of this category of 2D materials.…”

“…In fact, the recent progress of electronic and optoelectronic applications based on 2D materials have been well reviewed. [134][135][136] Here, we only review the device applications based on the utilization of intrinsic in-plane anisotropic properties of this category of 2D materials.…”

Recent Progress in 2D Layered III–VI Semiconductors and their Heterostructures for Optoelectronic Device Applications

“…In contrast to the usual 3D bulk semiconductors, 2D layered semiconductors have shown specific advantages for modern real device applications, such as atomic‐scale thickness, free of dangling bonds, good flexibility, atomic smoothness, etc . Particularly, the development of optoelectronic devices based on 2D semiconductors and their heterostructures is a rapidly expanding field thanks to their fascinating optical properties, with appreciable bandgaps covering from ultraviolet (UV) to infrared (IR) region . For example, a typical member of TMDs, 2D MoS 2 based photodetector has shown a large photoresponsivity of 880 A W −1 , and well‐defined electroluminescence (EL) spectra have been observed from the vertical heterostructure of WSe 2 /MoS 2 , revealing important potential for photosensing and light‐emitting diode (LED) applications …”

P‐GaSe/N‐MoS2 Vertical Heterostructures Synthesized by van der Waals Epitaxy for Photoresponse Modulation

“…2D p–n semiconductor heterojunctions, have emerged as the researching focus for both fundamental science and applied physics, which can combine the merits of different materials to achieve novel functions or modulate the photoelectronic properties of specific materials through high efficient charge transport at the interfaces of heterojunctions, thus having great potential in the field of microelectronics and optoelectronics such as photovoltaic devices, light emitters, tunnel diodes, and field‐effect transistors . Moreover, the built‐in potentials and interlayer recombination exhibited in the p–n junctions, determine the rectification characteristics, photovoltaic effects, and the photodetection capabilities, which show strong electrical tunability for electronic and optoelectronic properties .…”