Layered Metal Dichalcogenides-Based Hybrid Devices for Resistive Sensing
During the past few decades, photodetectors (PDs) are being regarded as the crucial components of many photonic devices which are being used in various important applications. However, the PDs based on the traditional bulk semiconductors still face a lot of challenges in terms of the device performance such as low responsivities, high response/recovery times, high power consumption, narrow detection range, and so forth. To overcome these limitations, a novel class of two-dimensional materials known as layered metal dichalcogenides (LMDCs) has shown great promise and the LMDCs-based PDs have been reported to exhibit competitive figures of merit to the state-of-the-art PDs. Moreover, the combination of LMDCs with conventional 3D semiconductors such as silicon and group III-Nitrides could extend the current technology towards novel device applications, and self-powered, broadband and ultrafast PDs can be realized. Among LMDCs, MoS2 and SnS2 are two semiconductors which show nearly extreme kind of behavior in terms of their electrical and optical properties. Therefore, a lot of room still exists to tailor the electronic and optoelectronic properties of MoS2 and SnS2-based PDs. Moreover, unlike other members of the LMDC family such as SnSe2, MoTe2, MoSe2, WSe2, and so on, MoS2 and SnS2 are free from toxic elements, and thus, environment-friendly semiconductors. Therefore, the present work focuses on the applications of the MoS2 and SnS2-based hybrid devices. In the present investigation, MoS2 has been grown on the different group III-Nitride semiconductors (AlN, GaN, InN) and the band alignment studies have been done for these three heterojunctions using the technique of high-resolution X-ray photoelectron spectroscopy. This has been followed by the implementation of one of these configurations i.e., MoS2/AlN for the realization of a self-powered, broadband and ultrafast PD. Further, the trade-off that usually exists between the broadband and wavelength-selective photodetection has been overcome via the phenomenon of polarity inversion exhibited by MoS2/GaN/Si-based PD. The device shows a positive photoresponse for the photons of ultra-violet region and exhibits negative photoresponse when the incident light changes to near infrared. After obtaining an excellent device performance by MoS2-based PDs, the optoelectronic properties of the less explored SnS2-based device have been investigated and the SnS2/p-Si-based device shows a high photoresponse with broadband photodetection. And finally, we have extended this work towards investigation of the humidity sensing behavior by SnS2 thin films of different thicknesses. All the devices exhibit a highly responsive behavior in self-powered mode, and a correlation between the sensitivity of the device with film thickness has been established. We believe that the present work can provide new routes towards the basic understanding of 2D/3D-based electronic and optoelectronic devices.