The band structures of the InAs/GaSb type-Ⅱ superlattice are investigated using the 8-band k.p method. The finite difference method (FDE) is used for solving the Schrödinger equation. It is found that a small variation in the valence band offset (VBO, one of the input parameters) could cause a great change in cut-off wavelength, especially at the long-wavelength range. We also developed a GUI application based on this method. Users could quickly get band structure details, such as bandgap energy, miniband energy, and wavefunctions with this GUI. The program and its code are available at https://github.com/STONEDIY/K.p-Mehtod-for-InAs-GaSb-Superlattice-Band-Structure-Calculation.
The pixel array of BSI CMOS image sensor is a kind of photoelectric device to obtain 2D image information. The image quality was evaluated by the modulation transfer function (MTF) of BSI CMOS image sensor pixel at Nyquist frequency. With the decreasing pixel size of BSI CMOS image sensor and the increasing spatial resolution, it is more and more difficult to improve the MTF at Nyquist frequency. According to the theoretical analysis, MTF is composed of aperture MTF and diffusion MTF, the comprehensive MTF function is usually obtained by the multiplication relationship between the two MTFs in the frequency domain. Aperture MTF and diffusion MTF have different influence factors and calculation functions, but they are related to the size of the opening. The opening here represents the sensitivity aperture and photo-sense region respectively. The smaller the opening of the detector pixel, the larger MTF will be. In this paper, the theoretical mechanism of MTF function is analyzed in detail, and the calculation results of MTF of BSI CMOS image sensor pixel under 8 typical optical wavelengths in 300nm-1000nm spectral band are listed.
Based on the working mechanism and characteristics of spaceborne hyperspectral Fourier transform infrared spectrometer, the computer and software were used as data acquisition and processing tools in this paper to study and simulate the various processes in photoelectric information processing of spectrometer. Analytical models including functional modules such as interference signal generation, effective signal detection, spectral data inversion and instrument error correction was established, then a visualization software system was developed. Finally, the accuracy of the model was calculated and optimized with experiments, the verification results show that this resolving system can process the interference data with high spectral resolution non-destructively, significantly improve the smoothness of the restored spectrum without distortion, and the measured spectral resolution of an instrument is better than 0.03cm-1 . This digital model could provide useful support for the design and parameter optimization of the aerospace Fourier transform infrared spectrometer.
Recently, type-II superlattice (T2SL) infrared detectors have drawn a lot of attention. Compared with II-VI-based HgCdTe materials, III-V-based T2SL materials (InAs/GaSb and related alloys) have higher quality, uniformity and stability. Besides, T2SL infrared (IR) detectors have flexibility in energy-band engineering. T2SL IR detectors have higher theoretically-predicted performance than HgCdTe IR detectors, and are commonly considered to be the most promising alternative for the state-of-the-art HgCdTe IR detectors. T2SL IR detectors have experienced significant progress over past few years, in areas of material epitaxy, band structure design, and device processing methods. On basis of summarizing and analyzing literature recently published, this paper presents the development history, current status and advanced technologies of T2SL IR detectors. We firstly introduce the T2SL material, working principle and its advantages. Then we review several band structures and advances of T2SL IR detectors in some famous research institutes. Finally, advanced T2SL technologies are presented, such as HOT (high-operating-temperature), dual-color and small SWaP (Size, Weight and Power) T2SL IR detectors.
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