Research On The High Quantum Efficiency Broadband Vis-SWIR InGaAs Photodetector

Recently,the mainstream low-light night vision devices are mainly equipped with super second-generation and third-generation image intensifiers,as well as Si-based devices for their high sensitivity in the visible-near infrared?Vis-NIR?spectrum.However,their respond spectrums cannot match with the short-wave infrared?SWIR?band of the atmospheric glow,which make it limited in moonless nights.The visible extended InGaAs focal plane arrays?Vis-InGaAs FPAs?working at room temperature has high sensitivity in the SWIR spectrum,which is expected to become an ideal choice of the next generation of low-light imaging equipment.In this work,the methods of fabricating high quantum efficiency broadband Vis-InGaAs FPAs and different types of anti-reflection coatings have been studied to satisfy the requirement of the night vision imaging.To improve the quality of imaging in low-light night vision environment,the model of quantum efficiency and the system of the measurement were introduced in detail firstly.The key factors affecting the QE of the broadband InGaAs detector are the concentration of absorption layer,the thickness of absorption layer and the thickness of InP contact layer.They were mainly analyzed in this paper.Based on the simulation results of Silvaco software,a structure of the InGaAs FPA with ultrathin contact layer thickness of?10 nm was innovatively proposed.The novel InGaAs epitaxial material grown by DCA equipment was partially characterized,such as Scanning Electron Microscope?SEM?,Photoluminescence Spectroscopy?PL?and X-ray diffraction?XRD?analysis,etc.,which provided for the preparation of high quantum efficiency broadband Vis-InGaAs detector.The critical process of fabricating Vis-InGaAs FPAs is precise thinning of?10 nm-thick InP contact layer.According to the analysis of the QE and the design of the detector structure,the key technologies to produce broadband Vis-InGaAs FPAs with high QE were explored further.The I-V characteristic curves of the detectors in different diffusion conditions were studied.The influence of the visible extension on the dark noise and dark current was explored,and the reasons behind these phenomenons were analyzed.A 160×120 broadband InGaAs FPA detector with a?10nm contact layer was prepared by using the inductively coupled plasma?ICP?etching technique to control the ultra-thin contact layer.A high QE of>60%over the Vis-SWIR spectrum?0.5?m-1.7?m?has been achieved finally,which verified the rationality of the design and the feasibility of the experimental method.In order to further improve the quantum efficiency of the device,the laminar anti-reflection coatings of the Vis-SWIR InGaAs FPA were explored in this paper.Based on Maxwell's equations,the equivalent principle of multilayer films was described in detail.The parameters of the multilayer films were designed and optimized by the Tfc simulation software combined with the structure parameters of the Vis-SWIR InGaAs detectors.The anti-reflection effect of multilayer anti-reflection films deposited on InP substrate by magnetron sputtering low temperature growth technique was also studied.Moreover,this anti-reflection technology was applied to the 160×120 Vis-SWIR InGaAs FPA detector modules based on etched surface.The films were respectively single layer?SiO₂=107 nm?and double layers?Zn S/SiO₂=44 nm/127 nm?.The changes of surface reflectance and current response of InGaAs FPA detectors before and after depositing anti-reflection films were compared,which showed the QE of the latter improved obviously.For example,the responsibility of the Vis-InGaAs FPA coated with Zn S/SiO₂ bilayer was increased from 0.83 A/W to 1.15 A/W at wavelength of 1500 nm.Benefiting from the anti-reflection coatings,high quantum efficiencies of66.23%@600 nm,95.91%@900 nm and 95.18%@1500 nm has been achieved.The subwavelength structure of three-dimensional all-dielectric material had a high integration degree and excellent anti-reflection effect,which provided a new anti-reflection method for improving the quantum efficiency of devices.In this paper,the refractive index gradient method was proposed for the Vis-SWIR InGaAs FPAs.The structure size of the SiN_X nano-cone was optimized by using FDTD Solutions,and the a mean reflectance of 5.4%within the full working spectrum of 0.4m-1.7m was obtained.Besides,the preparation method of nano-cone was also explored,and the morphology regulation of the nano-cone was realized by the second etching method.Besides,a s column-shaped nanoarray?CLNA?was designed for the traditional planar InGaAs FPA.FDTD Solutions software was used to simulate the influence of different size structures on reflectivity.After several optimizations,it was found that when the period of InP nanometer column was 600 nm,the side length was 360 nm,and the height was 200 nm,the reflectivity of InGaAs FPA detector was the lowest,with an average reflectivity as low as 3.07%between 900 nm and 1700 nm.Combining with Mie scattering model,the physical mechanism of InP nanometer column array was analyzed.Comparing the different preparation technology,the 160×120 InGaAs FPA detector integrated with InP CLNA was manufactured using electron beam lithography?EBL?and inductively coupled plasma?ICP?etching technology.The performance of the signal voltage and the QE was tested and compared between the FPA with and without InP CLNAs.It was shown that the QE of the InGaAs FPA with InP CLNAs reached@1200 nm,88.0%@1500 nm and 90.8%@1600 nm,respectively,which increased by 3.6%,11.2%and 15.0%compared with the FPA without nano structure.