Temperature-dependent laser beam-induced current (LBIC) measurements were carried out on planar In0.53Ga0.47As PIN photodetectors under both front-side and cross-sectional illumination over the range of 88-296 K. Combined with diffusion-mechanism simulations, the temperature-dependent carrier transport behavior under the two illumination configurations was analyzed comparatively. Opposite temperature dependences were observed in the extracted diffusion length, with the cross-sectional value increasing from 22.52 & micro;m at 273 K to approximately 125 & micro;m at 123 K, whereas the front-side value decreased from 18.69 & micro;m to 10.81 & micro;m. This difference is likely associated with the distinct carrier transport paths involved in the two configurations. The simulation results further suggest that the low-temperature attenuation of the front-side LBIC response is likely associated with the heterojunction barrier, while the built-in electric field provides only limited compensation. Overall, cross-sectional LBIC appears to more directly reflect intrinsic carrier transport in the InGaAs absorption layer.

To fabricate high-performance InGaAs infrared detectors, this paper employs metal-organic chemical vapor deposition (MOCVD) to prepare detectors on InAs0.6P0.4/In0.8Ga0.2As/InAs0.6P0.4 double-hetero structure materials, achieving a cutoff wavelength of 2.54 mu m. The photoelectric response characteristics of the detector were studied. Firstly, the performance differences of detectors with traditional structure and different grille-pixel structures are studied. Compared with the conventional structure, the average dark current density of the grille-pixel structures detector was reduced by 52.6%. Through the analysis of the dark current density components, the grille-pixel structure detector reduced the dark current density by suppressing the generation-recombination current density and the trap-assisted tunneling current density. Secondly, at room temperature, the peak detectivity of the detector of conventional structure is 4.58 & times; 1010 cm Hz1/2/W, while the average peak detectivity of the detectors of grille-pixel structure increases to 6.05 & times; 1010 cm Hz1/2/W, an increase of approximately 32%. Overall, the grille-pixel structure has successfully enhanced the critical performance of the detector.

Improved sensitivity of planar type extended-wavelength In0.75Ga0.25As/InP photodetectors is realized via post-diffusion rapid thermal annealing (RTA) treatment. The photoluminescence (PL) and x-ray diffraction characterizations are undertaken prior- and post- RTA treatments for a series of recipes with temperatures ranging from 500 to 750 degrees C and with durations of 15 and 30 s. While the dark current density at -10 mV decreases from 8.3 to 5.9 nA/cm(2) at 150 K for the RTA-processed sample as compared with the reference sample, the peak detectivity also rises from 9.0 & times; 10(9) to 2.0 & times; 10(10) cm Hz(1/2) W-1 at 150 K. Moreover, the cutoff wavelength remains unchanged whereas the strain of the lattice-mismatched epilayers tends to further relax post the RTA treatment. RTA temperatures higher than 750 degrees C leads to strong degradation of the PL intensity and fail of the photodetector. These results suggest that post-diffusion RTA is a feasible approach for the crystal lattice improvement of planar type extended-wavelength InxGa1-xAs (0.53 < x < 1) photodetectors.

Large dark currents currently limit the performance of InGaAs short-wave infrared (SWIR) detectors in aerospace remote sensing and night vision applications. To address this issue, SWIR detectors featuring various absorption layer doping concentrations and bilateral electrode configurations were fabricated on lattice-matched NIN InP/InGaAs/InP double heterojunctions via metal-organic chemical vapor deposition (MOCVD). Experimental and TCAD two-dimensional simulations demonstrate that increasing the absorption layer doping is the dominant factor, significantly reducing the total dark current density by ~96%. Mechanistic analysis indicates that increased doping in the absorption layer narrows the depletion region and prolongs the minority carrier lifetime, effectively suppressing both generation-recombination and trap-assisted tunneling currents. Concurrently, the bilateral electrode design distributes the electric field more uniformly, providing a further reduction in overall leakage. Furthermore, spectral analysis reveals that doping-modulated built-in electric fields lead to differentiated carrier collection mechanisms across varying wavelength bands. Ultimately, the optimized device achieves a peak detectivity of 2.28 × 1012 cm·Hz1/2W-1, representing an 82% improvement over low-doped counterparts and providing a crucial theoretical basis for the design of high-performance InGaAs detectors.

In this study,the simulation analysis and optimization of stray radiation in deep cryogenic Dewar components were conducted using a multiwave common optical path Dewar infrared system.The thermal radiation effects on the detector from key surfaces at different temperatures were analyzed using temperature field and dichroic surface simulations.Suitable cold transmission materials were selected,and Kovar was used for the cold platform,cold screen,and dichroic holder of the Dewar system.The effects of different blade levels and surface treatments of the cold screen on the point source transmittance were also evaluated.Based on these findings,the following optimization scheme was proposed:an elevated cold screen to block most of the radiation emitted or reflected by the window cap,adopting two levels of blades for the cold screen,and spraying graphene on the inner surface of the cold screen to improve the suppression of stray radiation.This scheme provides both theoretical and practical value for the design and application of low-temperature Dewar modules.

256 x 2 InGaAsP/InP Geiger-mode avalanche photodiode (GmAPD) arrays and a matched readout circuit with a triple-stage timing to digital converter (TDC) are realized. Pixels run asynchronously within the range gate of each frame, allowing measuring the time of flight of up to three reflected laser echoes. A mean array timing precision of 1 ns and a minimum hold-off time (T-hoff) of 64 ns are achieved. The measured mean dark count rates are 2.5, 1.0 and 0.5 kHz for the first, the second and the third stage TDC, respectively, under a mean photon detection efficiency (PDE) of 33.1% at 1064 nm, -20 degrees C and a T-hoff of 320 ns. While the cumulative afterpulsing probability (APP) exhibits strongly V-o- and T-hoff-dependent behaviors and a temperature-insensitive nature from -20 degrees C to 20 degrees C, a cumulative APP of 15% is obtained under a PDE of 20% and a T-hoff of 1 mu s. Photon count rate measurements indicate trade-off between the photon blockage and the increased afterpulsing probability under shorter T-hoff. Furthermore, capabilities of parallel acquirement of three-dimensional laser point cloud and two-dimensional photon count images are also demonstrated, highlights the superiorities of this multi-TDC scheme in both active and passive imaging under strong background interference.

Performances of In0.75 Ga0.25 As focal plane arrays (FPAs) with an extended cutoff wavelength of 2.2 mu m are remarkably improved by largely increasing the overshooting composition of the linearly-grading InxAl1-x As buffer layer. Zinc-diffused planar 640x488 FPAs with a pixel pitch of 23 mu m are fabricated on both the regular and the large overshooting epi-wafers with x=0.77 and x=0.85 for the end compositions of the linearly-grading InxAl1-x As, respectively. An order of magnitude lower dark current density of 1.1x10-10 A/cm(2) is achieved at 150 K for the large overshooting FPAs when comparing with 2.1x10-9 A/cm(2) for the regular FPAs. Suppressed dark signal and dark noise voltages are observed simultaneously over the measured whole integration time range. Moreover, the measured non-uniformity of the light response signal voltage drastically dropped from 16.4% to 2.9% while the peak detectivity substantially jumped from 7.1x10(12) to 1.8x10(13 )cmHz( 1/2) W-1. A signal to noise ratio enhanced laboratory imaging demonstration is also provided. These results suggest the large overshooting epitaxial technology can serve as a highly viable route for the lattice-mismatched InxGa1-x As FPAs towards further performance enhancement.

By adopting the vacuum sealed-ampoule technique, P-type doping of Zn elements in the lattice-mismatched N-InAs0.6P0.4/i-In0.8Ga0.2As/N-InP heterostructure material was achieved to form PN junction. The diffusion mechanism of Zn in the material was studied using secondary ion mass spectrometry (SIMS) and scanning capacitance microscopy (SCM). Furthermore, the temperature-dependent photoelectric properties were investigated after the short-wave infrared (SWIR) detector was fabricated and packaged in a vacuum Dewar. The results indicate that the doped Zn elements in the material are not fully activated, leading to a PN junction depth smaller than the diffusion depth, and rapid thermal processing (RTP) does not affect the PN junction depth. The cutoff long-wavelength of the detector at 273K is 2.53 mu m, and the peak detectivity reaches a peak value of 2.42x10(11) cm center dot Hz(1/2)/W at 133K.

The wafer bow caused by lattice mismatch between metamorphic InGaAs epitaxial layer and InP substrate has become one of the key factors limiting the large-scale development of extended wavelength InGaAs focal plane array photodetectors. By introducing tensile strain in InAlAs buffer layers and InAlAs cap layer to compensate the compressive strain caused by lattice mismatch, the wafer bow was decreased from 55.9 mu m to 22.2 mu m. The influence of strain compensation structure on the anisotropy of metamorphic InGaAs materials was investigated by stress distribution, surface morphology, and PL uniformity. XRD and PL characterizations indicate that small tensile strain in InAlAs buffer layers did not reduce the quality of metamorphic InGaAs epitaxial material. This study shows that strain compensation is an effective method to control wafer bow and decrease anisotropy of metamorphic InGaAs materials grown on InP substrate.

A diffusion barrier structure is proposed to control the accuracies of the Zinc diffusion velocity and depth for lightly doped short-wave infrared (SWIR) InGaAs planar photodetectors. By employing scanning capacitance microscopy and scanning electron microscopy characterizations, the Zinc diffusion profiles were investigated. The introducing of a moderately doped interlayer effectively tailored the diffusion front with reduced depth. In0.53Ga0.47As/InP PIN photodetectors with different structures were fabricated and characterized. Compared with the typical structure, the barrier detector exhibited a significantly lower dark current as well as an approximately three times higher peak detectivity. These results indicated that the diffusion barrier structure is promising for the fabrication of SWIR InGaAs focal plane arrays with both low capacitance and reduced dark current.

The pursuit of ultra-small pixel pitch InGaAs detectors necessitates a meticulous approach to addressing challenges associated with crosstalk reduction and dark current minimization. By developing the fabrication process technology of micro-mesa InGaAs detector, structures featuring a micro-mesa InGaAs photosensitive chip with 10 mu m and 5 mu m pixel pitch were successfully prepared. Subsequently, a comprehensive investigation was conducted to analyze the impact of the micro-mesa structure on crosstalk and dark current characteristics of the InGaAs detector. The obtained results revealed the efficiency of the micro-mesa structure in effectively suppressing crosstalk between adjacent pixels when the isolation trench etched into the absorption layer. However, a noteworthy challenge emerged as the fabrication processes induced material damage, leading to a considerable increase in recombination current and Ohmic leakage current. This adverse effect, in turn, manifested as a dark current escalation by more than one order of magnitude. The significance of these findings offers a novel perspective for the manufacturing of ultra-small pixel pitch InGaAs focal plane detectors.

The HgCdTe detector is the core device of the infrared imaging system, its reliability directly restricts the performance of the whole imaging system. For some special applications, it maintains in a non-operating storage state for a long time, it is significant to study its storage reliability. Due to the long lifetime of detectors, most studies have been conducted with accelerated life tests, there is a lack of experimental information concerning the failure of these detectors after longtime storage. In this article, the performance degradation of Hg1-xCdxTe detector with the 127 months long-term storage test is studied. The failure mode and failure mechanism of detectors are investigated through the statistics analysis and optical photomicrography. The results indicate that there are three failure modes, such as low-temperature opening circuit, chip circuit opening, and signal reduction accompanied by increased noise. The main type of failure is in the mode of signal reduction accompanied by increased noise, which is a typical failure mode for long-term storage of HgCdTe detectors. In this typical failure mode, corrosion products are observed near the photosensitive surface in the failure detector, which prove to be a metal product of indium. The long-term storage results can provide data support for accelerating storage test and improve the HgCdTe detectors design.

Si3N4 and Invar alloy brazed joints were achieved using two types of Ag-based interlayers: a Ag-Cu-In-Ti foil and a Ag-Cu-In-Ti/Cu/Ag-Cu multi-interlayer. The results showed that when only using a single Ag-Cu-In-Ti filler, the wave-shaped Fe2Ti + Ni3Ti intermetallic compounds are concentrated in the middle of the brazing seam. When adding Cu as the interlayer, the dissolution of the Cu interlayer formed a large number of Cu(s,s) blocks of different sizes in the brazing seam, which hindered the concentrated distribution of Fe2Ti + Ni3Ti intermetallic compounds in the brazing seam. As a result, Fe2Ti and Ni3Ti were dispersedly distributed in the brazing seam, increasing the shear strength of the brazed joint. The shear strength of brazed joints was increased by 82 % compared to joints brazed with a single Ag-Cu-In-Ti filler when the Cu interlayer was added.

Electron beam welding of pure molybdenum (Mo) and titanium alloy (Ti-6Al-4V) was performed with beam oscillation. The effects of beam oscillation with offset on the welded joints were analyzed in terms of microstructure, element distribution, chemical composition, microhardness, and tensile strength. The results showed that the fusion zone expanded with beam oscillation. Reaction layers were generated in both joints welded with and without beam oscillation. The thickness of the reaction layers decreased along the perpendicular direction. The reaction layers were (Mo, Ti) solid solutions. Both welded joints consisted of single-phase Mo, the β-Ti phase, and Mo-Ti solid solutions. The microhardness distribution of the joint welded with beam oscillation was more consistent than that of the joint welded without beam oscillation, and the maximum hardness was reduced from 340 HV to 270 HV. The tensile strength increased from 124 MPa to 204 MPa.

In the above article [1] , the affiliations were written as: The authors are with the State Key Laboratories of Transducer Technology, Key Laboratory of Infrared Imaging Materials and Detectors, Shanghai Institute of Technical Physics, Chinese Academy of Sciences, Shanghai 200083, China (e-mail: mayingjie@mail.sitp.ac.cn; lixue@mail.sitp.ac.cn).

为满足拼接式超大面阵型红外探测器的空间应用需求,超大规模冷平台组件需要在低温下工作,冷平台支撑结构需要较高的刚度以满足组件的抗振动性能,又需要较高的结构热阻以降低其传导漏热.提出了对称式八杆结构作为冷平台支撑,该支撑结构采用新型的高强度、低热导率的氧化锆陶瓷材料.基于有限元软件分析了支撑结构的高度、安装倾斜角度、宽厚比和材料对于组件的模态基频、支撑结构热阻以及组件在 30g静力学载荷下的最大应力的影响,通过对比选取了其中一组参数设计了实际的测试组件,支撑的结构热阻达到了 220 K/W,对组件进行了 5～2 000 Hz的正弦扫频试验、总均方根为 9g RMS的XYZ三个方向的随机振动等力学环境试验,最终组件通过了空间环境适应性试验验证,组件的基频达到了 560 Hz,并且测试结果与仿真结果趋势符合较好.结果表明:对称式八杆氧化锆支撑结构解决了超大面阵型红外探测器冷平台组件既需要高力学性能又需要低漏热的难题,满足工程化应用需求.

The joining of Si 3 N 4 and Mo using Ag–Cu–In–Ti active filler alloy with the brazing temperature ranging from 720 to 860 °C for 10 min is investigated in this article. The correlation between the joint strength and the microstructures of the brazed joints is discussed. In the results, it is shown that the activity of Ti is different at different temperatures, and thus the degree of diffusion of Ti to the interface is different. The activity of Ti gradually increases as the brazing temperature increases, and more Ti atoms diffuse into both sides of the base materials, resulting in a progressively thicker TiN + Ti 5 Si 3 reaction layer on the Si 3 N 4 ceramic side. Between 720 and 860 °C, the shear strength of the joint first increases and then decreases with brazing temperature. The maximum shear strength (223 MPa) is obtained at 830 °C.

Objective For some infrared (IR) optical systems, due to the wide field of view of the instrument, some cryogenic optical lenses must be packaged near the detector, otherwise the entire optical system will be very complicated. Moreover, for weak signal and multi -spectral detection, it is necessary to reduce the background. Except IR detectors, if several cold filters and lenses are housed in Dewar, then it is conducive to eliminating the infrared radiation background, improving system sensitivity and integration. This paper presents the package of mid -wave infrared (MWIR) and long -wave infrared (LWIR) detectors Dewar with integrated cryogenic optics. The micron -scale alignment requirement of a 32x4 array detector with a pitch of 120 mu m x 120 mu m and a dual -lens module at each band is comprehensively described. The key parameters such as detectors temperature uniformity, differential temperature packaging and low thermal mass are analyzed. We hope that Dewar package structure integrating 4 lenses, 2 optical filters and 2 detectors will be successfully developed. Methods First, several lenses and detectors are packaged, so the size of the Dewar cold platform is large, and the mass of the infrared detector Dewar cold finger and its top load reaches 364.7 g. If the acceleration in space application is 500 m/s(2), the maximum stress at the root of the cold finger can be calculated to be 352.9 MPa. In order to ensure the reliability under environmental vibration, it is necessary to use a new titanium alloy TC4 as the cold finger material, which can not only ensure sufficient mechanical strength, but also effectively reduce Dewar thermal loss. Secondly, in order to solve the problems of large longitudinal and axial thermal resistance between the detector, the cold lenses and the cold filter, as well as the low temperature uniformity of the detector array, both low thermal resistance heat transfer and the structure to realize differential temperature of the detectors are required. The cold platform is designed as the shared base of alignment for MWIR and LWIR detectors and cryogenic optics lenses. The structures of the sapphire cold link of the LWIR and the titanium alloy heat insulation ring of the MWIR are shown in Fig. 4. Through the combination of cold platform, sapphire cold link and titanium alloy heat insulation ring, the cooling capacity from the tip of cooler is non -uniformly introduced to the detector and the cryogenic optics lenses and filters, and the single -point cooling capacity is effectively transferred to different temperature zones. Thirdly, considering the material matching and assembly thermal stress of the detector at low temperature, the material whose linear expansion coefficient at low temperature matches the detector, lens, and filter is selected as the supporting structure material for assembling the cryogenic optics modules. The thermal stress simulation analysis of the infrared detector and optics is carried out, and the analysis results are shown in Fig. 6. The maximum cold shrinkage stress of the detector LWIR HgCdTe material is 15.8 MPa when it works at a low temperature of 65 K. Such a stress is relatively low. Results and Discussions The selection of titanium alloy cold fingers can not only ensure the mechanical reliability, but also reduce the heat conduction between the top of the cold fingers and the environment. Measured under liquid nitrogen environment, the thermal loss of titanium alloy cold fingers is about 160 mW smaller than that of stainless steel cold fingers. The brazing of the titanium alloy cold finger and the Kovar cold platform is realized by Ag-based solder. The weld structure after multiple temperature cycles from 300 K to 77 K is normal. The photo of the brazing sample is shown in Fig. 7. The average thermal loss value of the four Dewar assemblies tested at 77 K is 818.8 mW. In the orbit application, when the LWIR detector works at 65 K and the temperature window of Dewar is 195 K, the thermal loss is about 620 mW. In experiment, the LWIR detector works at 65 K, and its temperature uniformity is 0.08 K. Meanwhile, the temperature of the MWIR detector is about 73 K, and its temperature uniformity is 0.36 K. The temperatures of the long -wave lens 2 and lens 3 are stabilized at about 68 K and 70.5 K, and the temperatures of the mid -wave lens 2 and lens 3 are stabilized at about 80.5 K and 81 K, as shown in Fig. 10. According to the experimental data in Fig. 10, the longitudinal thermal resistance of the MWIR and LWIR detector -optics is relatively large. There is a bit difference about the temperature between the actual MWIR detector and the designed one, which should be related to too many heat transfer interfaces, the contact thermal resistance controlled by the screw torque during installation, and the shape of special heat -insulating titanium alloy TC4 rings. The adjustment of axial distance and pitch is adopted by partially adding different polyimide shims with the thickness of 5-20 mu m between the detector substrate and the cold shield, combined with assembly and testing by several instruments. Finally, the maximum measured value of alignment between the detector and the cryogenic optics lenses is 7.8 mu m, and the axial center deviation value between the detectors is 14.3 mu m.Conclusions This paper presents the MWIR and LWIR detectors Dewar assembly with integrated cryogenic optics. The new structures in Dewar such as monolithic cold platform and lens support (cold shield) with low thermal mass are designed to realize the alignment of single detector and its related cryogenic optics lenses, to solve the high -precision alignment between two detector -lens modules, and to solve new brazing processes of single high -strength cold finger and so on. This paper also proposes the key parameters of the Dewar such as detectors temperature uniformity, differential temperature packaging and low thermal mass. The thermal mass of Dewar at liquid nitrogen temperature is less than 0.85 W. The LWIR detector allows for focal plane array (FPA) operation at the temperature of 65 K, with a temperature uniformity of 0.08 K. Meanwhile, the MWIR detector is balanced at the temperature of 73 K, with a temperature uniformity of 0.36 K. The misalignment between the detector and the lenses is less than +/- 10 mu m, and the misalignment between two detector -lens modules is less than +/- 15 mu m. The Dewar integrating cryogenic optics has been testified by relevant environment reliability, and has been successfully applied to Geostationary Interferometric Infrared Sounder of the Fengyun-4 meteorological satellite.

根据"天问一号"火星矿物光谱仪短波红外探测组件小型化、轻量化、低功耗的需求,分析了红外探测器匹配性设计、集成式制冷机杜瓦适应性研制的难点.针对短波红外探测器高灵敏度、低温目标及多光谱探测需求的长积分时间模式的集成封装、抗大量级星器分离冲击等特点,提出了高信噪比探测器总体设计、具有噪声隔离和集成式冷平台结构设计、抗径向冲击的斜支撑结构设计等.解决了短波红外集成组件探测器低温下低热应力、长积分时间下干扰隔离、大量级力学加固、航天应用的高可靠性厚膜电路研制等关键技术.成功研制了短波碲镉汞探测器杜瓦制冷组件,并经过高低温循环、随机振动及机械冲击等严苛的空间环境热学力学适应性试验验证,试验前后组件性能未发生明显变化,满足火星矿物光谱仪工程化应用的要求.