| In order to improve the performance of transistors and the integration of electronic devices,the characteristic size of transistors is becoming smaller and smaller,which promotes the rapid development of semiconductors.However,as the gate length decreases,the transistor channel length also becomes shorter,which leads to the short-channel effect between source and drain,resulting in additional power consumption.However,if the thickness of silicon continues to shrink,it will produce a large number of defects on the silicon surface,unable to obtain a good quality crystal structure,seriously affecting the electrical performance of transistors.At this time,two-dimensional semiconductor materials have attracted wide attention in nanoelectronic devices,because of their ultra-thin characteristics,as well as excellent electrical and optical properties.In a large number of researches on two-dimensional semiconductor materials,molybdenum disulfide（Mo S2）,as a transition metal chalcogenide compound,has unique advantages such as suitable band gap,high field effect mobility and large switching ratio,and is a reliable candidate material for future metal oxide semiconductor field effect transistor（MOSFET）channel materials.The study of good contact between molybdenum disulfide and metal electrode can not only help solve the difficulties encountered in transistor scaling,but also show their good performance in different contact interfaces,which is the key factor to improve the performance of its transistors.The main contents of this paper are as follows:1.In our experiment,three different metal/semiconductor interfaces are prepared in the electrode engineering of Mo S2 MOSFET.The physical transfer of molybdenum disulfide to silver electrode（physical transfer device）by depositing silver（Ag）electrode on Mo S2（traditional thermal evaporation device）,and the insertion of ultra-thin alumina tunnel layer（alumina tunneling device）.The influence of different contact interfaces on the properties of transistors is also discussed.Thanks to the physical transfer method of Mo S2 onto Ag electrode（Mo S2/Ag）,the formation of metal-induced gap states and the introduction of defects can be inhibited.The average Schottky barrier height,contact resistance and carrier mobility of the physical transfer device reach the optimal level.They are 12.8 me V,0.45Ω·cm,and 68.36cm2 V-1 s-1,respectively,and have much better interface effects than the other two,providing a practical method for optimizing device performance.2.According to the height characteristics of Schottky barrier in different electrode engineering with traditional thermal evaporation and physical transfer methods,we used asymmetric electrode contact to deposit a silver electrode on one end of molybdenum disulphide and a silver electrode on the other end of physical transfer to prepare a photodiode with obvious rectifier characteristics.The device has a rectifier characteristic with an observable rectifier ratio of 102,a significant optical response characteristic,and an improvement of about an order of magnitude under negative leakage voltage.The ideal factor of photodiode is 1.3,light/dark ratio and responsivity are 0.9 and 26.51 A/W,respectively.This shows that a photocurrent is induced,which is typical of photodiodes.3.In order to achieve a very short contact length,we use the dislocation method so that the electrode width is only 0.3μm.On this basis,the Mo S2 MOSFETs with electrode widths of 0.3μm,0.5μm,1μm and 2μm were fabricated respectively,and their electrical properties were tested.By comparison,it is found that the contact resistance of 0.3μm ultra-short contact is the largest and the current is the smallest.The contact length of 0.5μm has the best performance,which is related to the transmission length.Finally,we calculate that the transmission length is about 0.43μm.This experiment paved the way for transistor scaling and has important significance in the field of reducing the contact length of two-dimensional transistors. |
