| In recent years,In As/Ga Sb Type-? superlattice infrared detectors have attracted wide attention from various research institutions at home and abroad,and large-scale,high-performance superlattice infrared focal plane detectors have developed rapidly.However,there are still some deficiencies in the material,such as the low absorption coefficient of the superlattice,resulting in low quantum efficiency of the detector.In order to improve the quantum efficiency,on the one hand,the thickness of the absorption region can be increased,but this method faces the problems of material growth quality and diffusion length limitation;on the other hand,a dielectric film can be grown on the surface of the detector,and the quantum can be improved by reducing the surface reflectance.Due to the low superlattice absorption coefficient and the influence of the highly doped In As Sb buffer layer,the response spectrum of the focal plane device with substrate removed will show obvious resonance cavity peaks,which have a great impact on the spectral response performance of the detector.Therefore,adjusting the spectral response and cut-off wavelength of the detector through the combination of the dielectric films and the detector,while improving its quantum efficiency is an important means to achieve a high-performance superlattice long-wave infrared detector.Although multi-layer film design has formed a relatively complete system after years of development,due to the complex structure inside the detector,the application of multilayer film on the detector is not a simple linear superposition.There are few related studies on the combination of detectors.Therefore,it is of great value and significance to study the effect of multilayer thin films on the performance of superlattice long-wave infrared detectors to realize the adjustment of the detector quantum efficiency and cut-off wavelength.The purpose of this subject is to adjust the response spectrum of the Type-? superlattice long-wavelength infrared detector.First,the parameters of the superlattice infrared detector are fitted through modeling and simulation,and then the different combination with the detector and multi-coatings is designed.The response spectra of the detectors with different multi-coatings grown on the surface were tested.Finally,the simulation and experimental results were compared and analyzed.The main research contents are as follows:1.Select the appropriate dielectric material by analyzing the refractive index,absorption coefficient,and own characteristics that the film material needs to meet in the experiment.According to the structure of In As/Ga Sb ? superlattice infrared long wave focal plane detector,the corresponding physical model is constructed in the Comsol software,and the boundary conditions and potential fields in the modeling process are optimized according to the actual conditions of the test to make the calculation result more accurate.In the process of fitting the detector parameters,firstly,the refractive index and absorption coefficient of the superlattice material were determined by analyzing the simulation and measured response spectra of the unit device ungrown In As Sb buffer layer,because the subsequent research content is to remove the substrate The overall design of the multi-coatings and the detector is implemented on the long-wave infrared focal plane device,so it is necessary to consider the influence of the In As Sb buffer layer in the long-wave infrared detector.Because of the influence of Si doping,its refractive index and absorption coefficient are difficult to determine.Then,by comparing and analyzing the simulation and measured response spectrum curves of the normal incidence device with the buffer layer grown under different parameters,the refractive index and absorption coefficient of the In As Sb buffer layer were determined.Further considering that the In As Sb buffer layer does not chemically react with the etching solution during the etching process.By comparing the response spectra obtained from the simulation and actual testing of the device under different thickness In As Sb buffer layers,the Parameters fitting of superlattice long wave focal plane detector in simulation are determined.2.After determining the parameters of the superlattice long-wave detector,the design and simulation of the combination of single-layer film and multi-layer film with the detector were carried out.Through the comparative analysis of the simulation results and the purpose of the experiment and the summary of the rules,the relevant parameters required for the subsequent experiments were determined.At the same time,in order to verify the simulation results,an experiment was also designed to grow multilayer films on the substrate.The results show that whether on Si or Ga Sb substrates,the simulation results and test results are in good agreement,and the device surface transmittance has been greatly improved.3.Multi-coatings designed by simulation is grown on the surface of the device,and the spectral response and dark current test of the device are performed.Experimental measurements: After growing a single layer of film on the surface of the device,it is more of a role to reduce reflection at a specific wavelength,which has little effect on the cut-off wavelength of the detector response spectrum and the overall response intensity;growing on the detector surface After the double-layer film,the 50% cut-off wavelength at 80 K was adjusted from 11.6?m to 12.5?m,and the peak response intensity was also improved;after three layers of film were grown on the surface,the cut-off wavelength was adjusted from 11.6?m to 12.3?m at 12?m Response intensity increased by 69%.Then it analyzes the error reasons of the simulation and actual test results,mainly from the aspects of device structure,process conditions,and simulation parameter fitting.Finally,by comparing the changes of the dark current before and after the growth of the multi-coatings,it was found that under the reverse bias there will be a certain effect on the dark current of the device,which may be caused by the stress and the defects caused during the multi-coatings growth. |
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