Effect of SiO2 encapsulation on the nitrogen reorganization in GaNAs/GaAs single quantum well

Effects of SiO2, encapsulation and rapid thermal annealing (RTA) on the optical properties of GaNAs/GaAs single quantum well (SQW) were studied by low temperature photoluminescence (PL). A blueshift of the PL peak energy for both the SiO2-capped region and the bare region was observed. The results were attributed to the nitrogen reorganization in the GaNAs/GaAs SQW. It was also shown that the nitrogen reorganization was obviously enhanced by SiO2 cap-layer. A simple model [1] was used to describe the SiO2-enhanced blueshift of the low temperature PL peak energy.

Hydrogen behavior in GaN epilayers grown by NH3-MBE

Hydrogen behavior in unintentionally doped GaN epilayers on sapphire substrates grown by NH3-MBE is investigated. Firstly, we find by using nuclear reaction analysis (NRA) that with increasing hydrogen concentration the background electron concentration increases, which suggests that there exists a hydrogen-related donor in undoped GaN, Secondly, Fourier transform infrared (FTIR) absorption and X-ray photoelectron spectroscopy (XPS) reveal Further that hydrogen atom is bound to nitrogen atom in GaN with a local vibrational mode at about 3211 cm(-1) Hence, it is presumed that the hydrogen-related complex Ga. . .H-N is a hydrogen-related donor candidate partly responsible for high n-type background commonly observed in GaN films. Finally, Raman spectroscopy results of the epilayers show that ill addition to the expected compressive biaxial strain, in some cases GaN films suffer from serious tensile biaxial strain. This anomalous behavior has been well interpreted in terms of interstitial hydrogen lattice dilation. (C) 2001 Elsevier Science B.V. All rights reserved.

有机氮的矿化进程及碳源添加的影响

本文运用室内恒温控湿好气培养试验研究了长期不同施肥制度培育的土壤有机N库的供氮能力；不同C／N比有机物料掺混土壤后有机N的矿化进程以及有机C源添加对其的影响。试验结果表明：长期不同施肥制度培育的土壤有机N库的供氮能力各不相同。与不施肥处理相比，长期施用化肥或有机肥均能提高土壤的供氮能力，但统计分析表明，长期单施化肥（150KgN·hm-2）与单施循环猪圈肥（约60Kg N·hm-2）处理土壤的供氮能力相似，说明有机培肥是保持和提高土壤氮素肥力的根本途径，而二者相结合可明显提高土壤供氮能力。掺混有机物料土壤中有机N的矿化进程与物料的C／N比密切相关，高C／N比的玉米秸粉能提供丰富的能源物质，但因其供应的氮素不足，微生物会固持土壤或空气中的氮而不发生有机N的净矿化释放，而低C／N比的大豆粉加入土壤后立刻会发生有机N的净矿化释放。有机C源的添加只能是暂时地抑制有机N的净矿化，但不能阻滞矿化过程的最终完成，土壤或有机物料中有机N的矿化分解是一个“持续进行、不可抑制的过程”。