Abstract:Cadmium zinc telluride (CZT) has excellent physical properties and can be used to prepare room-temperature nuclear radiation detectors and as substrate materials for mercury cadmium telluride infrared focal planes. Multiple methods can be used to grow CZT crystals, but the difficulty still lies in obtaining high monocrystal volume, low defect density single crystals. The traveling heater method (THM) is a major CZT crystal growth method, which has the advantages of low growth temperature, high single crystal yield, and good composition uniformity. A review was conducted on the growth of CZT crystals using the THM method, introducing its development history and related research results. Firstly, the basic principles and process flow of THM growth were introduced, followed by an explanation of the macroscopic morphology characteristics and key influencing factors during the growth process. Then, the correlation and suppression methods between Te inclusion defects and microscopic interface morphology were analyzed. Finally, the differences in Zn composition distribution between the THM method and the Bridgman method for CZT crystal growth were compared, highlighting the advantages of the THM method in macroscopic composition uniformity.

Abstract:The HgCdTe infrared detector chip with p-on-n structure has low dark current and long lifetime. It is the mainstream development direction of the high-performance infrared detector. In order to meet the development requirement of miniaturization of the future infrared detector, the p-on-n long-wave 1280×1024 detector with 10 μm pixel pitch was studied. In response to the difficulties of As ion implantation activation and long-wave small-pitch chip preparation technology, research and analysis have been conducted on As ion implantation technology and As activation annealing technology. The optimal conditions were verified by different characterization methods, and the detector chip was prepared through device technology. The I-V characteristic curve was tested, and a detector chip with good performance was obtained. This study is of great significance for the preparation of small-pitch long-wave p-on-n cadmium telluride mercury focal plane devices.

Abstract:Lead salt materials such as lead sulfide have attracted much attention in the field of uncooled infrared detection because of their low auger recombination coefficient. Chemical bath deposition method is widely used in the preparation of lead sulfide and other films. However, this method has the problem of uneven film growth on the graphical substrate. Based on the multi-exposure development technology, the influence of different pretreatment processes on the growth uniformity of the film on the graphical substrate was compared. The uniform growth of the lead sulfide film on the metal and insulating substrate surface was achieved. The results of the lead sulfide detector prepared by the optimal pretreatment method show that the photocurrent, responsivity and noise of the detector are significantly improved by the pretreatment of the graphic substrate, and the responsivity can be increased by 1.2 times. The preparation method of lead sulfide film provided in this paper can not only grow lead sulfide film with consistent uniformity on the graphic substrate, but also repair the damaged substrate, which is conducive to the integrated processing of the lead-sulfide-based focal plane array detector on the readout circuit surface.

Abstract:The surface temperature of Stirling cryocooler has a direct effect on the performance of infrared detector, so the optimization of the cooling design of Stirling cryocooler is particularly important in the thermal vacuum environment. In order to optimize the heat dissipation conditions of Stirling cryocooler applied in thermal vacuum environment, the thermal simulation analysis of the thermal vacuum environment of Stirling cryocooler based on the Ansys calculation platform is carried out, and the water-cooled heat dissipation fixture of Stirling cryocooler is designed. The simulation calculation and experimental research are carried out as well. The results show that the driving plate is the highest temperature position in the cryocooler. A water-cooled heat dissipation fixture with groove structure made of copper is designed, which can effectively reduce the surface temperature of Stirling cryocooler. Under the condition of constant external environmental temperature, the temperatures of Stirling cryocooler motor shell and the water-cooled heat dissipation fixture increase when the inlet temperature increases. Moreover, the temperature differences between inlet and outlet of the water-cooled heat dissipation fixture gradually decrease.

Abstract:The flip interconnect process is one of the key technologies for the preparation of infrared focal plane detectors. The Z-direction bias is an important factor affecting the yield of the flip interconnect process. From the point of view of the equipment of flip welding machine, the relationship between the level of flip welding machine and the Z-direction pressure deviation problem is discussed. The measured focal length values of different positions of the calibration block and the collimation cross position of the center point of the calibration block roughly indicate that the upper welding arm is relatively parallel to the lower abasement. In addition, the distances between the two standard blocks and the laser at different positions obtained by the laser beam accurately indicate that the upper welding arm is parallel to the lower abasement, and verify the accuracy of the levelling of the flip welding machine. The method system for studying the levelling problem of flip welding machine is established for the first time, which lays a good foundation for efficiently solving the Zdirection pressure bias problem of flip interconnection process and improving the yield and reliability of infrared focal plane detector.

Abstract:Electro-optic sampling (EOS) is often used to detect electric field waveform in the time domain of wideband terahertz radiation, and then it is also used to detect few-cycle laser pulse electric field waveform in the near-infrared to mid-infrared band. In this technique, the performance of electro-optic crystal directly affects its detection performance and frequency response bandwidth. In this paper, the frequency response characteristics and bandwidth of EOS based on lithium niobate crystal in the near-infrared band are studied, and the application of this technology in detecting few-cycle laser pulses is analyzed in detail, especially the distortion of few-cycle laser pulses caused by the detection process (including the changes of its center frequency and bandwidth). It is found that in the near-infrared band of 900－2500 nm, the measurement error of the few-cycle pulse with 1.5 oscillation cycles depends on the crystal thickness and the laser wavelength to be measured. When the crystal thickness is 10 μm, the deviation between bandwidth and center frequency is less than 1%. When the crystal thickness is 100 μm, the resulting maximum deviation of bandwidth is 25% and the maximum deviation of center frequency is 10%. For the few-cycle pulse with 2.5 oscillation cycles, the deviation of bandwidth and center frequency is obviously reduced. This paper provides a good theoretical reference for measuring the electric field waveform of few-cycle laser pulses in near-infrared band by means of EOS crystal.