Silicon Based Transition Metal Dichalcogenides Photodetector

Photodetector is widely used in our production and daily life.In visible light,the main material for photodetector is silicon.However,in order to achieve some specific functions,such as expanding the detection range,we need other materials combining with silicon.But it is difficult for other 3D materials to integrate with silicon.In the past few years,graphene and transition metal dichalcogenides?TMDCs?has attracted tremendous interest because of their exotic electrical and optoelectrical properties.These two-dimensional?2D?crystals share the common feature with the intra-layer covalent bond and inter-layer van der Waals bond.The lack of surface dangling bonds not only allows them to be easily stripped down to atomic-scale thickness but also can be readily integrated into any other substrates.Especially,most of TMDCs have small band gaps?1.06-2.88 eV?.Therefore,those TMDCs can be used as visible light absorbers for photodetecting application.It is known that junction-based photodiode is one kind of important photodetectors.For TMDCs-related planar structure photodetectors,there are two categories,one is TMDCs-TMDCs?2D-2D?and the other is TMDCs-conventional materials?2D-3D?.Here,we report the fabrication and photoreponse properties of n-Si/Graphene and n-Si/WS₂ heterojunction photodiode.Firstly,we fabricated a n-Si/Graphene Schottky junction using wet etching.Then we studied the photoelectric properties and the I-V curve at different temperatures of the Schottky junction.We found that our device show great properties: photoresponse0.5 A/W,and responsetime 164 ?s.Besides our device appeared breakdown at low temperature.The explanation was given through the contrast experiment.Secondly,improving the production technology,discarding the wet etching steps,we fabricated the n-Si/WS₂ heterojunction structure,and studied its photoelectric and temperature properties: photoresponse 1.2 A/W,and responsetime 8 ?s.Because of the improvement of fabrication process,this device no longer appear breakdown.Then we focused on the study of the origin of high photocurrent.We found that if the applied voltage was large enough,the non heterojunction region still had a large photocurrent,but its responsetime was slower than the heterojunction region.Besides,we studied the performance of our device with modified carbon quantum dots.The device showed improving photoresponse in each wavelength.At last,we fabricated p-Si/WS₂ heterojunction for studying the breakdown characteristics.And it was found that the photo response of the device was about 5.6A/W,near the zener breakdown point.