| As optical detecting technology is a core technology in advanced manufacturing,artificial intelligence and other information technology fields,photodetectors are widely applied to military,national defence,industrial production,national economy,scientific research,medical equipment and optical communications.Nevertheless,there are many shortcomings in traditional silicon-based photodetectors due to the limitations of light absorption and band-structure of silicon materials.In recent years,emerging graphene-silicon heterojunction photodetector have attracted the attention of many researchers for its excellent rectification characteristics,high response,high detectivity and high stability.Up to now,the peak responsivity(-0.73 A W-1)of graphene-silicon heterojunction photodetector has surpassed the responsivity of traditional silicon-based PIN photodetectors.Moreover,the graphene-silicon heterostructure photodetector has more extensive application prospects for its simpler structure,easier processing and lower cost than traditional silicon-based PIN photodetector.In order to further improve the performance of the silicon-graphene heterojunction photodetector,this paper has carried on the following work:Firstly,the device structure of graphene-insulator-silicon(GIS)tunneling photodetector was designed and optimized.The GIS tunneling photodetector was developed through introducing a nanoscale insulating layer at silicon-graphene interface of graphene/silicon heterostructure photodetector,and the insulator films was deposited by atomic layer deposition(ALD)to achieve thickness control of the films.After comprehensive consideration,AlN,Al2O3 and SiO2 were selected as the tunneling layer material and the thickness of the tunneling layer were optimized in the experiment.According to the experiment results,it can be concluded that the AlN film with thickness of 15.3 nm is the most appropriate tunneling layer of GIS tunneling photodetector in this study.Secondly,the photo-detection properties of the optimized GIS tunneling photodetector was further characterized and the photocurrent multiplication mechanism was discussed.As a result,the graphene-AlN-silicon tunneling photodetector performed excellently under both dark condition and illumination.Compared with graphene-silicon photodetector,the dark current of the tunneling photodetector was suppressed by about an order of magnitude compared with graphene-silicon photodetector,while a broad-spectrum optical responsivity enhancement was achieved at the same time.Under 850 nm incident light,the responsivity of the GIS tunneling photodetector with 15.3 nm AlN tunneling layer is as high as 3.95 A W-1 and the external quantum efficiency is up to 580%.The high optical gain of this tunneling detector is derived from the high electric field of tunneling layer and the impact ionization during photogenerated carrier tunneling process.Thirdly,self-assembly silicon dioxide microcavity array was researched to enhance light response of silicon-based PIN photodetectors.The performance results of devices confirmed that multi-band optical response enhancement was achieved in the photodetectors modified with siicon dioxide dielectric microcavity array,and the responsivity in some spectral range has been increased by more than 20%.Meanwhile,other properties such as breakdown voltage,dark current,junction capacitance of the modified photodetector showed no difference from control sample.This research has developed a new silicon-based tunneling photodetector with simple structure,excellent performance and high optical gain,and the photocurrent multiplication of this G-I-S tunneling junction was experimentally verified and theoretically analyzed.In addition,this study also developed a low-cost,simple and effective method to enhance the light absorption of photodetectors through the dielectric microsphere array,which has broad commercial application prospects. |
PDF Full Text Request