Research Article Cite This: ACS Appl. Mater. Interfaces XXXX, XXX, XXX−XXX
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Ultrasensitive 2D/3D Heterojunction Multicolor Photodetectors: A Synergy of Laterally and Vertically Aligned 2D Layered Materials Jiandong Yao, Zhaoqiang Zheng, and Guowei Yang* State Key Laboratory of Optoelectronic Materials and Technologies, Nanotechnology Research Center, School of Materials Science & Engineering, Sun Yat-sen University, Guangzhou 510275, Guangdong, P. R. China
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ABSTRACT: In this work, a p-type 2D SnS nanofilm containing both laterally and vertically aligned components was successfully deposited on an n-type Si substrate through pulsed-laser deposition. Energy band analysis demonstrates a typical typeII band alignment between SnS and Si, which is beneficial to the separation of photogenerated carriers. The as-fabricated p-SnS/n-Si heterojunction photodetector exhibits multicolor photoresponse from ultraviolet to near-infrared (370−1064 nm). Importantly, the device manifests a high responsivity of 273 A/W, a large external quantum efficiency of 4.2 × 104%, and an outstanding detectivity of 7× 1013 Jones (1 Jones = 1 cm Hz1/2 W−1), which far outperforms state-of-the-art 2D/3D heterojunction photodetectors incorporating either laterally or vertically aligned 2D layered materials (2DLMs). The splendid performance is ascribed to lateral SnS’s dangling-bond-free interface induced efficient carrier separation, vertical SnS’s high-speed carrier transport, and collision ionization induced carrier multiplication. In sum, the current work depicts a unique landscape for revolutionary design and advancement of 2DLM-based heterojunction photodetectors. KEYWORDS: 2D layered materials, SnS, 2D/3D heterojunction, photodetectors, pulsed-laser deposition, multicolor photodetection
1. INTRODUCTION The unprecedented merits of 2D layered materials (2DLMs) such as strong light-matter coupling,1,2 favorable bandgap,3,4 dangling-bond-free surface,5−8 high carrier mobility,3,9−16 excellent durability for bending,17,18 and good integrating compatibility19−21 have established them as having the most potential as building blocks, outperforming traditional 3D bulk materials toward for next-generation optoelectronic devices. Although planar metal−semiconductor−metal 2DLM photodetectors feature high responsivity,22−28 heterojunction photodetectors possess unique attributes of low dark current, appreciable signal-to-noise ratio, ultralow energy dissipation, fast response/recovery speed, and incomparable synergistic effect.29−32 To date, numerous hybrid 1D/2D, 2D/2D, and 2D/3D heterojunction photodetectors have been successfully fabricated,33 among which 2D/3D heterojunction photodetectors have proven as a potential scheme for the following reasons. On one hand, 2D/3D stacks possess light absorption much stronger than that of ultrathin 1D (2D)/2D stacks,34 laying solid foundation for generating photocarriers. On the other hand, 2D/3D heterojunction photodetectors can be readily achieved by directly integrating 2DLMs onto mature 3D commercial substrates such as Si and GaAs,19,31 which circumvents the onerous transfer and alignment process for fabricating 1D (2D)/2D heterojunction photodetectors.35−37 In fact, thus far, intensive effort has been devoted to 2D/3D heterojunction photodetectors.32,38 For example, by transferring graphene on Si, An et al. fabricated an ultrasensitive © XXXX American Chemical Society
graphene/Si heterojunction photodetector, which achieved a high responsivity of 0.33 A/W.20 In addition, by directly growing MoS2 on Si, Wang et al. fabricated a MoS2/Si heterojunction photodetector, which achieved an extremely high detectivity of 1013 Jones (1 Jones = 1 cm Hz1/2 W−1).21 Despite the considerable progress, previous investigations merely focus on 2D/3D heterojunction photodetectors incorporating either laterally or vertically aligned 2DLMs. Thus far, there have been no attempts to construct 2D/3D heterojunction photodetectors incorporating both laterally and vertically aligned 2DLMs, although such investigation is not only fundamentally important but also critical to unlock unprecedented photosensitivity of 2DLMs. In this contribution, tin monosulfide (SnS), an IVA−VIA 2DLM with a large light absorption coefficient and a high theoretical carrier mobility,39 was successfully grown using pulsed-laser deposition (PLD). The PLD-grown SnS nanofilm contains both laterally and vertically aligned components. Importantly, the as-fabricated p-SnS/n-Si heterojunction photodetector demonstrates multicolor photodetection from ultraviolet (UV) to near-infrared (NIR) (370−1064 nm). Moreover, it manifests a high responsivity of 273 A/W, a large external quantum efficiency (EQE) of 4.2 × 104%, and an outstanding detectivity of 7× 1013 Jones, which far outperforms Received: June 21, 2018 Accepted: October 16, 2018 Published: October 16, 2018 A
DOI: 10.1021/acsami.8b10396 ACS Appl. Mater. Interfaces XXXX, XXX, XXX−XXX
Research Article
ACS Applied Materials & Interfaces state-of-the-art 2D/3D heterojunction photodetectors incorporating either laterally or vertically aligned 2DLMs.
2. EXPERIMENTAL SECTION In this work, SnS nanofilm was grown using a PLD-450a deposition system. SnS target was purchased from Beijing Founde Star Science & Technology Co., Ltd. Its purity was 99.99%. The Sn:S atomic molar ratio was 1:1. SiO2/Si (n-type,
