Design Of GaAs-Al MSM Device And Capillary Force Assisted Femtosecond Laser 3D Micro/Nano Processing

GaAs is a kind of semiconductor belongs to III-V compound material,which has the advantages of wide band-gap,high breakdown voltage,strong radiation resistance and stable chemical property.The GaAs devices perform outstandingly in the sensitivity of device responsiveness,linear response and comprehensive performance.Metal-semiconductor-metal(MSM)is attractive because of its plane structure,fabrication simplicity,and easiness of integration.So,GaAs-based photo-detector has been one of the most popular research topics in recent years.The electro-optical properties of GaAs-based MSM devices were studied in this paper.Firstly,the basic structure and working principle of MSM detector are discussed,and the methods of improving the performance of MSM photoelectric detector are proposed.Then,the influence of the structure parameters of A1 Grating MSM detector on the performance of the device is studied using FDTD simulation.Results show that the performance of Al grating MSM detector is comparable with Au grating MSM detector,and at the wavelength of 600 nm-750 nm,A1 grating detector performs better than Au grating detector.In addition,A1 grating MSM detector can significantly reduce the cost of production due to the low price of Al.Good micro and nano structure is a prerequisite for many cutting-edge breakthroughs in science,and it has been a hot spot to explore the fabrication method of micro and nano structure in the world.Two-photon polymerization(TPP)induced by femtosecond laser is a powerful and potential technology to fabricate 3D micro/nanostructures of various materials such as polymers,hybrid materials,organically modified ceramics,and metals,which has the advantages of short function time,small heat-affected zone and high precision in the fabrication process.And it has been applied to microoptics,electronics,communications,biomedicine,microfluidic devices,MEMS and metamaterials.High quality 2D and 3D micro and nano devices have been fabricated using femtosecond laser direct writing.In this paper,various structures were fabricated using femtosecond laser and capillary force self-assembly.The prerequisition of self-assembly:FC>FE was discussed.Random imperfections in pillar structures or instabilities in the evaporating process result in the random of assembled pattern of the symmetric square arrays.To reduce the formation of these unwanted irregular structures and to provide a level of control over the self-assembly process,one possible method is to introduce an additional spacing,Ad,between separate self-assembled sets.Results indicate that the method is feasible to produce robust,uniform,and ordered assemblies.In addition,as Ad increases,the yield rate of the expected tells rises sharply,until reaching 100%.Diverse patterns were fabricated by introducing the additional space.Then,anisotropic structures were fabricated owing to the gravity-governed capillary force difference,and anisotropic structures could also be achieved because of height induced capillary force difference,or diameter induced capillary force difference.Double-layer structure was fabricated by femtosecond laser direct writing,and the upper layer can be assembled under the influence of capillary force.The influence of based-pillar diameter and laser power on the structure was discussed,and the results of self-assembly of upper pillars under different power and height were analyzed.Two possible applications of self-assembly were introduced,one is selective trapping and releasing of microparticles,in which microparticles with different sizes can be trapped by tuning the intracell pitches accordingly;Crystallization is another possible application,when two pillars cells were designed to be closer to each other,micro lines are able to grow from mother solution with a higher concentration.Femtosecond laser printing with capillary force and solution evaporation self-assembly technology opens a new gallery to fabricate novel 3D microstructures and micro/nanoparticles of different materials and may find numerous applications in the communities of chemistry,biomedicine,and microfluidic engineering.Possible applications will be find in chemical and biomedicines.