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The effects of tensile stress induced by SiO2 passivation layer on AlxGa1−xN∕GaN heterostructure photodiode are investigated. The photodiode, with SiO2 layer annealed at 650°C for 30min in O2, shows that reverse current has decreased to 6.16nA∕cm−2 under −10V, two orders lower than that of the device without annealing technique. The responsivity also increases to 0.212A∕W at zero bias. The high-resolution x-ray diffraction, Hall measurements are taken to investigate the surface strain and electrical properties of p-AlGaN surface. These observations indicate that tensile stress induced by SiO2 annealing technique can improve performances of this photodiode greatly.

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The origin of the lower minority carrier lifetime in the border region of multicrystalline silicon (mc-Si) ingots was investigated. Based on minority carrier lifetime measurements and chemical analyses, distributions of defects and impurities were studied. It is found that the content of oxygen, carbon and other metal impurities in the border region were almost at the same level as that in the bulk, while the concentration of Fe-B pairs is significantly higher. More interestingly, the dislocation density in the border region was observed to be much lower than that in the adjacent part. It is elucidated that the lower dislocation density in the border region leads to more iron existing in the form of Fe-B pairs, which could be responsible for the low lifetime. In addition, it is shown that the low minority carrier lifetime in the border region can be improved effectively by phosphorous gettering.

Independent dedicated ventilation system is an advanced air conditioning system developed in last few years. There is little research on the design of the system at present. This paper establishes control equation of flow and temperature field based on the energy transmission theory and simulates heat pipe independent dedicated ventilation system using special flow field numerical simulation software. In pretreatment process of FLUENT, this paper uses unstructured six prisms and parallelepiped grid and encrypts grid which makes the result of calculation is more accurate. The simulation uses residual of 10-5 high precision to calculate, and obtains the residual convergence curve. Curve analysis shows that the calculation is very reliable and stable. In post-treatment process, it uses FLUENT results processing module, obtains the temperature flow pattern of heat exchanger independent dedicated ventilation system. We take one of the root canal for analysis. The result shows that the temperature in both sides of the tube is higher, and the temperature through the tube and close to the wall part is lower. It is coincide with the actual working condition of tube ventilation and heat dissipation outside the pipe. This result proves the accuracy of the numerical simulation and provides the reliable theory basis for the design of heat pipe heat exchanger independent dedicated ventilation system.