High-Performance Photodetectors Using Transition Metal Dichalcogenide (TMD)-based Hybrid Structures

Abstract

Since the era of graphene, atomically thin transition metal dichalcogenides (TMDs) with a two-dimensional (2D) semiconducting layered structure have recently received increasing attention as suitable materials for post-silicon electronics and optoelectronics due to their exceptional electrical, mechanical, and optical properties. Particularly, TMDs present different energy band gaps depending on the type of TMDs and also exhibit strong optical absorption and ultrafast charge transfer, thereby providing many opportunities for researches in various optoelectronic devices, including photodetectors, solar cells, and light-emitting diodes. However, despite their superior optical properties, it is difficult for TMDs to absorb sufficient light due to their atomically thin body thickness, consequently restricting the successful integration of TMD-based optoelectronic device applications. In this light, various studies have been performed to improve the characteristics of TMD-based optoelectronic devices (especially photodetectors) through their hybrid structure, by applying the doping[1] or absorbing[2] (with very high absorption rate) layers, or inserting a passivating[3] layer (with suppression of carrier scattering), eventually improving the collection of photo-generated carriers.Here, we demonstrate a high-performance TMD-based (WSe2 and ReSe2) photodetectors with a very high photoresponsivity (1.27×106 A/W for WSe2 and 1.18×106 A/W for ReSe2) and fast temporal photoresponse (rising/decaying time: 2.8/20.8 ms for WSe2 and 58/263 ms for ReSe2). This high-performance was accomplished by (i) applying a triphenylphosphine (PPh3)-based n-doping layer and (ii) inserting the passivating layers (hexagonal boron nitride (h-BN) or (3-aminopropyl)triethoxysilane (APTES) layers). The observed n-doping concentrations (Δn) were approximately 1.02 – 7.77×1011 cm-2 for TMD layers. By performing the PPh3-based n-doping process, the photoresponsivity of the TMD photodetectors increased (from 2.70×103 to 4.31×105 A/W for WSe2 and from 3.97×103 to 3.68×104 A/W for ReSe2). In particular, by additionally inserting a h-BN layer at the WSe2/SiO2 interface and an APTES layer at the ReSe2/SiO2 interface, we eventually obtained a very high photoresponsivity of 1.27×106 A/W for WSe2 and 1.18×106 A/W for ReSe2 while maintaining the other performance parameters (photoresponse times and photodetection range).[1] D.-H. Kang, J. Shim, S. K. Jang, J. Jeon, M. H. Jeon, G. Y. Yeom, W.-S. Jung, Y. H. Jang, S. Lee, J.-H. Park, ACS Nano 2015, 9, 1099.[2] S. H. Yu, Y. Lee, S. K. Jang, J. Kang, J. Jeon, C. Lee, J. Y. Lee, H. Kim, E. Hwang, S. Lee, J. H. Cho, ACS Nano 2014, 8, 8285.[3] S. Wang, X. Wang, J. H. Warner, ACS Nano 2015, 9, 5246.