Study On Hot Carrier Emission Broad-band Infrared Detector Based On Schottky Junction

Thanks to the rapid development of semiconductor materials and device technology,photodetectors based on photovoltaic effect can perfectly cover multiple bands from ultraviolet,visible to mid and far infrared.Among them,the infrared detector is particularly attractive,which has many key applications in medical and health,environmental monitoring,military reconnaissance and so on.Currently,commercial infrared photodetectors generally adopt narrow band gap materials,which have to resort to precise band?gap engineering of the components of compound semiconductors for realizing photoelectric conversion in the infrared regime.Due to the requirements of lattice matching,the epitaxy growth of such materials is difficult and the process is complex.Meanwhile,the large scale array photodetection needs to be integrated with the silicon CMOS readout device.All these factors inevitably lead to high material and process costs in modern infrared detector technology.In the past few years,the plasmonic hot carrier emission in metals has attracted extensive attention worldwide in the field of nanophotonics.By integrating metal nanostructures on silicon substrate to form Schottky junction,a new photoelectric conversion way based on hot electron emission is developed.The photoresponse of silicon-based hot carrier detector is due to the intraband excitations within the conduction band,which can overcome the silicon band-gap absorption limit(1100 nm)and extend the cut-off wavelength to communication and even mid-infrared band.Silicon based hot carrier detector can be fabricated easily via standard planar fabrication processes that fully compatible with CMOS technology.Moreover,the hot carrier device can be designed elegantly to embrace the freely manipulated spectral,polarization and EM-field characteristics.With the added values in multifunctional integration,the plasmonic hot carrier mediated detection is expected to become an alternative strategy for future silicon-based infrared detection.However,regarding on the extremely low quantum efficiency of the reported plasmonic detectors in literatures,there is still an urgent requirement to explore the performance enhancement strategies through systematic optimization of the structural,optical and electrical properties.To this end,focusing on the metal-semiconductor Schottky barrier modulation and the losses associated to hot carrier transport/emission,this paper conducts a comparative study on the performance of various plasmonic metals for infrared photodetection.The main works of this paper include the following three parts:(1)In order to understand and fit the measured results,we construct the corresponding theoretical models to mimic the behaviors of nanophotonic structures and the hot carrier related transport/emission process.The impact of the reverse voltage biasinginduced image force barrier lowering on the photocurrent output is also discussed.(2)Based upon above experimental and theoretical frameworks,the detection efficiency of hot carrier devices employing different plasmonic metals is studied.The experimental measured results are analyzed and discussed in the perspectives of materials' loss mechanism and metal-semiconductor barrier height manipulation.(3)The design,fabrication and performance analysis of a MetalSemiconductor-Metal(MSM)photoconductive type device,aiming at high photocurrent responsivity via photoconductive mechanism.