Asymmetrically Encapsulated Vertical ITO/MoS₂/Cu₂O Photodetector with Ultrahigh Sensitivity

Abstract

Strong light absorption, coupled with moderate carrier transport properties, makes 2D layered transition metal dichalcogenide semiconductors promising candidates for low intensity photodetection applications. However, the performance of these devices is severely bottlenecked by slow response with persistent photocurrent due to long lived charge trapping, and nonreliable characteristics due to undesirable ambience and substrate effects. Here ultrahigh specific detectivity (D*) of 3.2 × 10 Jones and responsivity (R) of 5.77 × 10 A W are demonstrated at an optical power density (P ) of 0.26 W m and external bias (V ) of -0.5 V in an indium tin oxide/MoS /copper oxide/Au vertical multi-heterojunction photodetector exhibiting small carrier transit time. The active MoS layer being encapsulated by carrier collection layers allows us to achieve repeatable characteristics over large number of cycles with negligible trap assisted persistent photocurrent. A large D* > 10 Jones at zero external bias is also achieved due to the built-in field of the asymmetric photodetector. Benchmarking the performance against existing reports in literature shows a viable pathway for achieving reliable and highly sensitive photodetectors for ultralow intensity photodetection applications.

High Responsivity and Photovoltaic Effect Based on Vertical Transport in Multilayer α‐In2Se3

“…The presence of a finite bandgap in these 2D semiconductors (except monolayer graphene) makes them promising for visible and infrared (IR) photodetectors with excellent spectral response and gain while the flexibility of transferring them on any substrate without being plagued by lattice mismatches provides an excellent platform for heterogeneous and extreme bandgap engineering. Graphene, transition metal dichalcogenides (TMDs), and black phosphorous and their heterostructures exhibit intriguing material behaviors, which are strongly dependent on the number of layers (or thickness) and have attracted the attention of the device community toward multifunctional optical devices . Viable device technologies would require multilayer or even bulk 2D layered materials for higher light absorption; however, most of these materials including the most widely studied MoS 2 exhibit indirect bandgap in their multilayer configurations which is a bane for optoelectronic applications …”

“…Graphene, transition metal dichalcogenides (TMDs), and black phosphorous and their heterostructures exhibit intriguing material behaviors, which are strongly dependent on the number of layers (or thickness) and have attracted the attention of the device community toward multifunctional optical devices. [3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18] Viable device technologies would require multilayer or even bulk 2D layered materials for higher light absorption; however, most of these materials including the most widely studied MoS 2 exhibit indirect bandgap in their multilayer configurations which is a bane for optoelectronic applications. [19][20][21][22][23] One of the promising van der Waals layered materials from the III-VI group is indium selenide (In 2 Se 3 ) which has the potential to show exceptional photoresponse from visible to near-infrared wavelength.…”

Light emission from the layered metal 2H-TaSe2 and its potential applications

“…Two-dimensional layered materials have recently attracted a lot of attention as active material in photodetector applications [39][40][41] . Vertical heterojunction photodetectors based on ultra-thin twodimensional layered materials provide a number of advantages 5,42 compared to lateral structures, namely (1) ultra-short carrier transit time due to nanometer separated electrodes, which is difficult to achieve otherwise in a lithography limited planar structure; (2) large built-in vertical field; (3) suppression of series resistance due to improved carrier collection efficiency that is not limited by transfer length; and (4) repeatable characteristics where encapsulated photoactive layer does not degrade from ambience effects and screened from substrate induced traps.…”

“…In general, obtaining a low resistance electrical contact without destroying the high quality of ultra-thin 2D active layers remains an outstanding challenge for 2D materials. Recently, vertical electronic and optoelectronic devices 1,[4][5][6] using layered materials are becoming increasingly popular as they exploit carrier transport through these nanometer-thick active layers-something that is difficult to achieve in a lithography limited conventional planar structure. Maintaining the pristine nature of the layers underneath the contact becomes even more crucial in the context of these vertical devices where the contact physically sits right on top of the active layers.…”

Self-Powered, Highly Sensitive, High-Speed Photodetection Using ITO/WSe2/SnSe2Vertical Heterojunction

“…Further, unlike bulk semiconductors, different layered materials can be seamlessly integrated in a vertical heterojunction stack without having to worry about the lattice mismatch between two materials [2]- [4]. Consequently, TMDCs (such as MoS 2 , MoSe 2 , WS 2 and WSe 2 ) have been extensively explored in the recent past as promising candidates to achieve low cost, sensitive photodetectors [5]- [14].…”