Two dimensional Grafen/ReSe2/ReS2 photodetector fabrication and characterization

As part of the thesis, the structures of p-cSi/PSi/ReS2/graphene and graphene/ReSe2/ReS2 were simulated using the SCAPS-1D software package. For the simulated graphene/ReSe2/ReS2 structure, higher performance was achieved compared to the p-cSi/PSi/ReS2/graphene structure. At 550 nm, an EQE of 96.37% was achieved, and at 790 nm, a responsivity of 0.54 A/W was obtained. For this reason, the graphene/ReSe2/ReS2 structure was experimentally produced. Additionally, in addition to this structure, graphene/ReSe2/ReS2/graphene was experimentally fabricated and investigated. The 2D ReSe2 and ReS2 used in the fabrication were synthesized via the CVD method. The CVD method was preferred due to its capability to produce high-quality ReX2 structures with scalable growth suitable for device applications. The graphene electrodes were derived from commercially purchased graphene films. These films were transferred onto a SiO2/p-Si substrate using PMMA-assisted wet transfer. Subsequently, graphene stripes of the desired dimensions were patterned using photolithography and ICP-RIE etching. The ReSe2 and ReS2 flakes, grown in a controlled manner via the CVD technique to suit the device architecture, were sequentially stacked over the graphene stripes on the SiO2/p-Si substrate using PDMS-assisted dry transfer. After metallization, the photodetector structure was completed. A comprehensive literature review revealed no prior studies investigating the graphene/ReSe2/ReS2/graphene and graphene/ReSe2/ReS2 device architectures. The fabricated graphene/ReSe2/ReS2 photodetector demonstrated broadband photodetection performance from the visible to near-infrared spectral range (510 nm-1550 nm). This broadband response is attributed to the photon absorption and carrier generation by the graphene at frequencies beyond the cut-off of the ReSe2 and ReS2 layers, indicating that graphene functions not only as an electrode but also as an active photodetection layer at higher frequencies. A high responsivity of approximately 10^4 A/W was achieved with the fabricated photodetector. As a result, an EQE of 4.8×10^4 % and a detectivity of 3.6×10^12 Jones were calculated. Additionally, it was observed that the fabricated device could operate in a self-driven mode without requiring an external power supply. The ability of the device to detect across a broad wavelength range is significant for applications in advanced technologies such as quantum communication, autonomous vehicles, smart agriculture, night vision systems, and space or satellite-based sensing. Moreover, its self-powered operation highlights its potential for energy efficient optoelectronic applications.