Wet etching and passivation of GaSb-based very long wavelength infrared detectors

The etching and passivation processes of very long wavelength infrared (VLWIR) detector based on the InAs/GaSb/AlSb type-II superlattice have been studied. By studying the effect of each component in the citric acid solution (citric acid, phosphoric acid, hydrogen peroxide, deionized water), the best solution ratio is obtained. After comparing different passivation materials such as sulfide + SiO₂, Al₂O₃, Si₃N₄ and SU8, it is found that SU8 passivation can reduce the dark current of the device to a greater degree. Combining this wet etching and SU8 passivation, the R₀A of VLWIR detector with a mesa diameter of 500 μm is about 3.6 Ω ·cm² at 77 K.     

微藻生物固碳技术进展和发展趋势

大气中CO2含量升高是导致温室效应的主要原因,因此,减少CO2的排放和积累是解决全球气候变暖的重点.传统的CO2减排方法包括捕集(capture)和储存(storage),涉及化学吸附、物理吸收、膜分离和低温蒸馏等一系列物理化学方法,但其均存在成本高和不可再生等缺点.通过种植或养殖生物质可以捕集CO2.微藻生长周期短、光合效率高,其CO2固定效率为一般陆生植物的10~50倍;同时微藻生长速度快,能利用不可耕地,具有广阔的发展前景.本文概述了适用的藻种及所能达到的CO2固定效果,分析了光生物反应器类型、光照强度、光周期、温度、pH、CO2浓度、CO2吸收效率、气体传质效率和营养需求(包括来自市政和工业农废水中的N、P等营养)等多种因素对微藻固碳效果的影响.最后,对微藻固碳的实际应用和经济可行性进行了评估,展望了微藻固碳技术的发展和应用前景.     

Growth of high material quality InAs/GaSb type-II superlattice for long-wavelength infrared range by molecular beam epitaxy

By optimizing the V/III beam-equivalent pressure ratio, a high-quality InAs/GaSb type-II superlattice material for the long-wavelength infrared (LWIR) range is achieved by molecular beam epitaxy (MBE). High-resolution x-ray diffraction (HRXRD), atomic force microscopy (AFM), and Fourier transform infrared (FTIR) spectrometer are used to characterize the material growth quality. The results show that the full width at half maximum (FWHM) of the superlattice zero-order diffraction peak, the mismatching of the superlattice zero-order diffraction peak between the substrate diffraction peaks, and the surface roughness get the best results when the beam-equivalent pressure (BEP) ratio reaches the optimal value, which are 28 arcsec, 13 arcsec, and 1.63 Å, respectively. The intensity of the zero-order diffraction peak is strongest at the optimal value. The relative spectral response of the LWIR detector shows that it exhibits a 100% cut-off wavelength of 12.6 μm at 77 K. High-quality epitaxial materials have laid a good foundation for preparing high-performance LWIR detector.