The HgCdTe Photodiode is the most basic and important unit of HgCdTe IRFPA (Infra-red focal plane array) detectors, which have been widely used in the fields of security, fire protection, remote sensing and deep space detection. For HgCdTe IRFPA, the trapped charges of the HgCdTe material and the ionic charges introduced during the preparation process are the factors, other than environmental stress, that have the greatest impact on IRFPA performance. The trapped charges come from the trap energy level in the HgCdTe material, which exist during the crystal growth process and can be improved by adjusting the growth conditions, but it cannot be completely avoided. The ionic charges introduced during the process are generally concentrated at the interface and surface of the HgCdTe material, which can be reduced by process improvement, but cannot be completely avoided. In order to analyze the mechanism of multiple charges affecting the HgCdTe detector performance, a type of n+ -on-p HgCdTe Photodiode is selected as the object of this work, and the effects of the concentration and distribution of charges on the carrier distribution and energy band structure of the n+ -on-p HgCdTe are analyzed in detail. The introduction of additional net charge relative to an ideal n+ -on-p HgCdTe Photodiode leads to the aggregation or scavenging of local carriers and affects the energy band structure near the charge, creating additional potential barriers or potential wells, which is likely to cause device degradation. On this basis, the optoelectronic properties of the HgCdTe Photodiode have been investigated under infrared radiation at a wavelength of 9.5 μm, as the light I–V characteristics, the dynamic resistance–voltage characteristics, band structure and carrier density distribution. According to the results of this work, the quasi-fixed charges introduced by defects or contamination will directly affect the generation rate of photogenerated carriers and affect the I–V and R–V characteristics of the HgCdTe Photodiode, leading to phenomena such as rising dark currents, decreasing spectral response, and decreasing quantum efficiency.
The waveguide branch plays an important role in integrated photonic circuits by dividing input light into two or more output lights, thereby facilitating optical power distribution and mode selection. Ordinary optical waveguides used in waveguide branches suffer from excessive optical loss and narrow branch angles, limiting their effectiveness in mode selection among other problems. Photonic crystals are constructed by arranging macroscopically homogeneous dielectric (or metallic) materials into periodic arrays, with carefully designed internal defects that provide them with frequency-selective and spatial properties. In this study, a silicon-based wide-angle waveguide branch composed of two-dimensional photonic crystals has been successfully created. The branch is capable of separating two wavelengths of light, namely 850 nm and 950 nm, by adjusting the positions of silicon cylinders in the two-dimensional photonic crystal with the purpose of optimizing optical power at different wavelengths. The silicon-based wide-angle waveguide branch is expected to be employed in multimode optical communication systems. Its utilization will contribute towards the reduction in size and complexity of integrated optical communication systems, while enhancing system reliability.
HgCdTe infrared focal plane array imaging detectors have been widely used in a variety of fields such as night vision surveillance, remote sensing mapping and astronomical observation. In recent years, with the development of semiconductor manufacturing processes, the array size of HgCdTe IR focal plane array imaging detectors has gradually increased, and the preparation process has become increasingly complex. During the preparation process, impurity ions can enter the HgCdTe material and cause degradation of device performance or even device failure. This work investigates the distribution of impurity elements in HgCdTe IR focal plane array detectors prepared by both processes and the mechanism by which impurity elements cause device failure.
Cryogenic Infrared Rays Focal Plane Array (IRFPA) detectors have been widely used in industry, transportation, security monitoring, meteorology and medicine because of the high sensitivity and temperature resolution. For HgCdTe IRFPA detectors, the typical working temperature is about 80 K. To make the IRFPA detector works at low temperatures, the detector should be integrated on a Dewar cold platform, whose refrigeration power would be higher than the heat load of the IRFPA. In general, the IRFPA detector and the Dewar cold platform would be integrated together to form a Dewar assembly at room temperature. In addition, the materials in IRFPA have different thermal expand coefficients, it means the thermal mismatch in the IRFPA would be an unavoidable issue in work. The thermal strain has a significant effect on the solder joints in switching cycle, which could lead to the creep strain and thermal fatigue crack. With the increase of the switch cyclic number, the creep strain and thermal fatigue crack under the thermal stress would lead to the failure of solder joints. Therefore, the low temperature thermal strain in switching cycle can affect the reliability of IRFPA detectors. So, the low temperature thermal strain and the creep lifetime of solder joints has been researched.
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