Optimization of Metamorphic InGaAs Quantum Wells on GaAs Grown by Molecular Beam Epitaxy

We investigate the molecular beam epitaxy growth of metamorphic InxGal-xAs materials （x up to 0.5） on GaAs substrates systematically. Optimization of structure design and growth parameters is aimed at obtaining smooth surface and high optical qualdty. The optimized structures have an average surface roughness of 0.9-1.8 nm. It is also proven by PL measurements that the optical properties of high indium content （55%） InGaAs quantum wells are improved apparently by defect reduction technique and by introducing Sb as a surfactant. These provide us new ways for growing device quality metamorphic structures on GaAs substrates with long-wavelength emissions.     

Optical Properties of Highly Strained GaInAs／GaAs Quantum Wells Grown by Sb Assistance

Optical properties of highly strained GaInAs/GaAs quantum wells (QWs) grown by molecular beam epitaxy with Sb assistance are investigated. The samples grown by Sb incorporation and Sb pre-deposition methods display high room-temperature photoluminescence (PL) intensity at extended 10ng wavelength. This result is explained by the surfactant effects of Sb during the growth of GaInAs/GaAs QW systems. An abnormal Sshaped temperature dependence of the PL peak position is found in the In0.42Ga0.58As/GaAs triple QWs sample grown with Sb pre-deposition. By investigating the transmission electron microscope images and time-resolved PL spectra, it is found that the S-shaped temperature dependence of the PL peak position originates from the exciton 10calization effect brought by the Sb-rich clusters on the QW interface.     

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.     

关于农村安全饮水工程管理的探讨

农村饮水安全工程建设后管理应以保障农民群众的饮水安全为目标,以提供优质供水服务为宗旨,坚持按经济规律办事。建立适应社会主义市场经济体制要求、符合农村饮水工程特点、产权归属明确、责任主体落实、责权利相统一、有利于调动各方面积极性、有利于工程可持续利用的管理体系;按成本水价供水、计量收费、市场运作,确保农村人畜饮水工程长期发挥效益,为建设社套主义新农村奠定基础。本文主要介绍了当前农村饮水工程管理存在的问题,并提出了相应的解决措施。     

Influence of Growth Parameters of Frequency-Radio Plasma Nitrogen Source on Extending Emission Wavelengths from 1.31 μm to 1.55 μm GaInNAs/GaAs Quantum Wells Grown by Molecular-Beam Epitaxy

High （42.5%） indium content GaInNAs/GaAs quantum wells with room temperature emission wavelength from 1.3μm to 1.5μm range were successfully grown by Radio Frequency Plasma Nitrogen source assisted Molecular Beam Epitaxy, The growth parameters of plasma power and N2 flow rate were optimized systematically to improve the material quality. Photoluminescence and transmission electron microscopy measurements showed that the optical and crystal quality of the 1.54μm GaInNAs/GaAs QWs was kept as comparable as that in 1.31 μm.     

膜供氧催化氧化处理太空舱冷凝废水研究

采用膜供氧催化氧化反应器处理太空舱冷凝废水。以乙醇为目标污染物,研究了膜供氧催化氧化反应器对其的处理效果,并考察了催化反应对膜传质模型的影响。结果表明,随着停留时间的增加,乙醇的去除率增大,中间产物乙酸的生成率减少。当废水流量为0.5mL·min-1,气室压力为2kPa时,乙醇的去除率可达86.1%,其中81.4%完全氧化,4.7%转化成乙酸。基于传质模型对实验结果分析表明,催化反应有利于提高膜供氧总传质系数,当流量为0.5mL·min-1时,与无催化反应条件相比,氧总传质系数提高11.8倍。停留时间的增加也有利于提高膜供氧传质系数。结果表明,膜供氧催化氧化反应器可高效降解冷凝废水中的乙醇,在太空舱冷凝废水处理中有潜在的应用价值。     

Metamorphic InGaAs Quantum Well Laser Diodes at 1.5μm on GaAs Grown by Molecular Beam Epitaxy

We report a 1.5-μm InGaAs/GaAs quantum well laser diode grown by molecular beam epitaxy on InGaAs metamorphic buffers. At 150K, for a 1500×10μm^2 ridge waveguide laser, the lazing wavelength is centred at 1.508 μm and the threshold current density is 667 A/cm^2 under pulsed operation. The pulsed lasers can operate up to 286 K.     

氧化钙(100)、(110)和Ca-terminated(111)表面性能的第一性原理研究

【目的】对氧化钙(100)、(110)和Ca-terminated(111)的表面能、表面弛豫及电子结构进行系统研究。【方法】运用基于密度泛函理论的第一性原理计算体系的表面性能,计算过程采用6层原子和15真空层的Slab模型。【结果】计算得到的氧化钙体相晶格常数合理地符合实验值。氧化钙(100)面的表面能最低因而最稳定,更容易暴露。(110)面表面能介于(100)和Ca-terminated(111)面之间,Ca-terminated(111)面的表面能最高而最不稳定。(100)表面弛豫程度最弱,Ca-terminated(111)表面弛豫程度最明显,而(110)表面弛豫程度则介于(100)和Ca-terminated(111)面之间。(100)表面Ca-O和Ca-Ca之间的电子云强烈重叠,共价成键特征突出,稳定性高。Ca-terminated(111)表面只存在Ca-Ca原子间电子云重叠,且杂化程度明显变弱,因此Ca-terminated(111)面的稳定性最低,(110)面的稳定性居于(100)面与Ca-terminated(111)面之间。【结论】氧化钙中(100)面的表面稳定性能最好,(110)面次之,Ca-terminated(111)面稳定性最差。     

High-density and narrow size-distribution InAs quantum dots formed by a modified two-step growth

We develop a modified two-step method of growing high-density and narrow size-distribution InAs/GaAs quantum dots (QDs) by molecular beam epitaxy. In the first step, high-density small InAs QDs are formed by optimizing the continuous deposition amount. In the second step, deposition is carried out with a long growth interruption for every 0.1 InAs monolayer. Atomic force microscope images show that the high-density ($\sim $5.9$\times $10$^{10}$\,cm$^{ - 2})$ good size-uniformity InAs QDs are achieved. The strong intensity and narrow linewidth (27.7\,meV) of the photoluminescence spectrum show that the QDs grown in this two-step method have a good optical quality.