Structure Design And Preparation Of GaN-based UV-IR Dual-color Integrated Photocathode

With the rapid development of semiconductor industry and detection technology,people are no longer satisfied with the detection of monochromatic light band,and gradually turn the exploration direction to the detection of dual-color or polychromatic light band;At present,with the continuous maturity of semiconductor material growth and preparation technology,there are more and more reports related to dual-color integrated photodetectors.Group III nitrides represented by GaN have the advantages of wide band gap and high saturation electron rate,and the spectral range can cover near infrared to terahertz.They are widely used as inter subband optoelectronic device materials.With the research and development of group III nitride quantum well infrared detection,GaN based materials have gradually become the first choice for the preparation of dual-color integrated photocathodes.At present,although the UV-IR dual-color integrated photoelectric solid-state detector is developing rapidly,the UV-IR dual-color integrated photocathode is still in its infancy.In this paper,the structural design,subband transition theory,optical simulation,preparation technology and photoelectric characteristics of GaN based UV-IR dual-color integrated photocathode are studied.Firstly,according to the theories of semiconductor photoelectric emission and quantum mechanics,a new type of p-doped GaN based quantum well ultraviolet infrared dual-color integrated photocathode structure is designed,its detection mechanism and material characteristics are briefly described,and the working model of dual-color integrated photocathode is established.Secondly,through the simulation and comparative analysis of the performance of the photocathode by Silvaco TCAD software,it is found that the peak spectral response of the structure is about 60 m A/W at 220-260 nm in the ultraviolet band,0.06 m A/W at 0.8 ? and0.35 m A/W at 1.8 ? in the infrared band,and has the characteristic of "solar blindness" in the visible band.Subsequently,the optimal parameter range of the epitaxial layer is determined by optimizing and simulating the cathode structure.Thirdly,select a group of epitaxial layer parameters to grow the cathode structure,use the characterization tool to characterize and test the structure,prepare the solid-state detection device through the process,and test its spectrum.The spectral response value of the structure is 9m A/W at 253.7nm in the ultraviolet band and 0.012 m A/W at 780 nm in the infrared band.It has the characteristic of "solar blindness" in the visible band.In the subsequent Cs/O activation test of the grown original film,it is found that there is a spectral response peak of about 25 m A/W at 250 nm in the ultraviolet band,and it has the characteristic of "solar blindness" in the visible band.The overall spectral response change trend is basically consistent with the simulation results;However,due to the influence of test conditions,no signal was measured in the near-infrared band.Fourthly,a quantum cascade structure is proposed on the basis of quantum wells,and a new type of p-doped NEA QCD GaN/AlGaN UV-IR dualo-color integrated photocathode structure is designed.The simulation shows that the peak spectral response of the structure is about 60 m A/W in the ultraviolet band 220-260 nm,0.30 m A/W in the infrared band 1.8? and has the characteristic of "solar blindness" in the visible band.Subsequently,the optimal parameter range of the epitaxial layer is determined by optimizing and simulating the cathode structure.