| InGaAs is an ideal material for short-wave infrared imaging,due to its low dark current,high detection rate,high working temperature and good anti-radiation,etc.It showed a great application value.With further demand in space remote sensing and imaging applications,advanced InGaAs detector with higher performance,lower cost and lower power consumption becomes the focus of future development.For extended wavelength InGaAs detectors??cutoff >1.7?m?,due to lattice mismatching between absorbption layer and InP substrate,which would cause more dislocation and defects in the absorption layer,make a large dark current.So,studying on the relationship between material and detectors,characterizing of micro photosensitive area of device,optimizing device process parameters to improve device performance are very important.In this paper,extended wavelength InGaAs detector photosensitive area defects,material quality,key of material parameters and process optimization were studied,and some certain results were achieved.We carried out the characterization study about extended wavelength InGaAs materials by using x-ray.The InGaAs materials were characterized by high-resolution x-ray and synchrotron radiation,respectively.The experiment obtained that the In0.83Ga0.17 As absorption layer FWHM is 737.2arcsec,and In0.83Ga0.17 As epitaxial layer lattice mismatch in the vertical direction is 1.945%,1.928% lattice mismatch in horizontal direction.Using 10 KeV synchrotron radiation x-ray experiment obtained that the digital gradient superlattice layer?DGSL layer?cycle is 104.9?,having a good consistency with the TEM tests results.At the same time,a variety of materials have characterized by the grazing incidence test.The test results found that when the incidence angle is 0.3 degrees,the signal strength was biggest,and when the incident angle is greater than 0.7 degrees,the signal was not detected.The higher 18 KeV synchrotron radiation x-ray experiment study showed that the original single substrate peak divided into multiple overlapping peak.In order to study the minority-carrier diffusion length of the materials,the nondestructive SPV test method was performed for two different doping concentration of normal InGaAs material.The experiment obtained that the high doping concentration sample minority-carrier diffusion length is 5.59?m,the low doping concentration sample is 6.3?m.The detectors prepared by different processes were used as the research object to study the defect information of the micro-photosensitive area of the In0.83Ga0.17 As detector.The electron beam induced current?EBIC?and deep energy level transient?DLTS?method were used to characterize the defects of the detector,and the effects of different processes on the device performance were also studied.EBIC results showed that sample A?rapid thermal annealing after mesa etching?and sample B?rapid thermal annealing before mesa etching?percentage of defect,defect number and defect density was 13.09%,96,23.3×106 cm-2 and 7.33%,34,8.14×106cm-2,respectively.The three test samples tested by DLTS method were: 1#?Cl2/N2 etching?and 2#?Cl2/CH4 etching?device for conventional SiNx passivation device,3#?Cl2/CH4 etching?device for optimizing SiNx passivation device.The results showed that sample 1 existed a minority-carrier?hole?defect,with the trap position 124 meV,the capture cross-section 5.77×10-19cm2,the defect concentration 1.34×1014cm-3.Sample 2 and sample 3 existed a majority-carrier?electronic?defect,with the trap position 432 meV and 45 meV,the capture cross-section 9.31×10-15cm2 and 4.65×10-20cm2,the defect concentration 1.61×1014cm-3 and 2.91×1014cm-3,respectively.The defect density was different because the DLTS tested the deep level defects of the sample and the EBIC tesed the electrical activity of sample surface defects.The effect performance of device about two processes that rapid thermal annealing before and after mesa etching was studied.It turned out that rapid thermal annealing before mesa etching of the photodiode has a lower dark current and a lower area-dependent dark current component.The processes that using Cl2/N2 and Cl2/CH4 etching gas respectively were studied.By using PL,transmission line model?TLM?,IV characteristics and detectivity of device to value the advantages and disadvantages of two etching samples.The results showed that the PL signal intensity is weaker,the square resistance Rsh obtained by TLM model is larger,dark current density is lower,the signal is larger and the detectivity is higher for the Cl2/CH4 etching sample.So,the Cl2/CH4 etching process is better than the Cl2/N2 etching process.The above-mentioned annealing optimization process and etching optimization process were used to verify the integration of the device.By fabricating corresponding photodiodes,testing dark current of the devices under different temperature and bias,analyzing of thermal activation energy of the devices.The research results showed that the dark current density of the optimazition process sample is?387nA/cm2?lower than the conventional process sample?1.2?A/cm2?,so the annealing etching process compared with the conventional process has a certain advantage.We have carried out high-density extended wavelength In0.83Ga0.17 As devices exploration research based on the background of InGaAs detector aerospace application.And we have developed successfully the high-density sub-10?m pitch In0.83Ga0.17 As detector.Obtaining the In0.83Ga0.17 As detector with the scale 10×10,photo-sensitive element area 9?m×9?m,10?m pitch and the duty ratio of 81%.The experiment obtained the dark current density is 1.47×10-4 A/cm2 at 300 K and 10.5nA/cm2 at 200 K for the sub-10?m pitch In0.83Ga0.17 As detector.The sample of cutoff wavelength at room temperature is 2.57?m obtained by spectral response testing. |
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