| Ultraviolet photodetectors(UV PDs)respond to ultraviolet light and convert optical signals into electrical signals and they can be used in military and daily life widely.The MSM(Metal-Semiconductor-Metal)is one new structure of photodetector.Compared with other structures,the MSM photodetector has the advantages of high responsiveness,small dark current,fast response speed,and small surface capacitance.With the progress of semiconductor technology,the size of lithography,nano imprinting and other process can be achieved in nanometer level.In recent years,in order to enhance the performance of UV PDs,,many surface micro/nano structures have been introduced into MSM photodetector,such as nanoholes,nanopillars,nanowires and so on.At the same time,the excitation of local surface plasmons(LSP)by metal nanoparticles is beneficial to enhancing the light responsivity of PDs.Among them,the LSP resonance wavelength of Al and Ag nanoparticles is in the range of ultraviolet,which has great significance for the research of UV photodetectors.The work of this thesis can be mainly divided into the following contents:1.Study on the Position and Intensity of LSP Extinction Peak for Al and Rh Metal Filled Nanopore Arrays.Based on the enhancement of the nanopore and metal nanoparticles to the MSM UV PDs,we got the idea of filling metal materials into nanopore array what we called metal filled nanopore array.Then,we simulated Al and Rh metal-filled nanopore arrays by FDTD solution,calculating their extinction spectrum and changes of surrounding electric field on the range of 200 nm to 700 nm.After adjustment,it was found that the LSP extinction peak of these two metal-filled nanopore arrays can reach up to deep ultraviolet and get greater intensity.Meanwhile,the local electric field at resonance wavelength appeared to be significantly enhanced,which made a positive effect on the separation of acupuncture-electron pairs.Further,we tried to change various parameters of the metal-filled nanopore array,including the radius,depth,spacing,shape,etc.,and explored the factors that control the position and intensity of extinction peaks.The simulation results showed that the radius and spacing of nanopores got good job in regulating the position of extinction peaks.In terms of intensity,if the depth of nanopores increase,the intensity of extinction peaks will show the same trend while positions are not changed.For Al metal,circular and hexagonal nanohole arrays can obtain good extinction peaks in deep ultraviolet band while quadrilateral and circular nanohole arrays are more suitable for Rh metal.In addition,the method of incident light source from the back can increase the intensity of deep ultraviolet extinction peaks more than 10%.This study provides theoretical guidance for the preparation of metal filled nanopore array MSM UV Photodetector.2.Study on ?-Ga2O3/GaN heterojunction MSM dual-band UV PDs with built-in electrodes.The conventional ?-Ga2O3/GaN heterojunction MSM dual-band UV PDs are affected by the thicker ?-Ga2O3 layer.The photo-generated carriers in the GaN layer need to tunnel through the thicker ?-Ga2O3 layer,and then,absorping by electrodes which form a photocurrent gain.Therefore,we built the built-in metal electrode in the?-Ga2O3 layer through lithography,ICP etching,magnetron sputtering and other processes to reduce the tunneling difficulty of photo-generated carriers from GaN layer.Compared with conventional PD,the maximum responsivity of built-in electrodes PD is 0.89A/W for 362nm ultraviolet light,which is 22 times than conventional devices.It proved that the built-in electrodes have a positive effect on the collection of photogenerated carriers in deep layer.Conducive to the future research on the responsivity of MSM PDs with quantum wells and superlattice structures. |
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