An Anomalous Gain Mechanism in GaN Schottky Barrier Ultraviolet Photodetectors

The gain mechanism in GaN Schottky barrier ultraviolet photodetectors is investigated by focused light beam. When the incident light illuminates the central region of the Schottky contact electrode, the responsiyity changes very little with the increase of reverse bias voltage. However, when the incident light illuminates the edge region of the electrode, the responsivity increases remarkably with the increase of reverse bias voltage, and the corresponding quantum efficiency could be even higher than 100%. It is proposed that the surface states near the edge of the electrode may lead to a reduction of effective Schottky barrier height and an enhancement of electron injection, resulting in the anomalous gain.     

Evaluation of both composition and strain distributions in InGaN epitaxial film using x-ray diffraction techniques

The composition and stain distributions in the InGaN epitaxial films are jointly measured by employing various x-ray diffraction (XRD) techniques, including out-of-plane XRD at special planes, in-plane grazing incidence XRD, and reciprocal space mapping (RSM). It is confirmed that the measurement of (204) reflection allows a rapid access to estimate the composition without considering the influence of biaxial strain. The two-dimensional RSM checks composition and degree of strain relaxation jointly, revealing an inhomogeneous strain distribution profile along the growth direction. As the film thickness increases from 100 nm to 450 nm, the strain status of InGaN films gradually transfers from almost fully strained to fully relaxed state and then more In atoms incorporate into the film, while the near-interface region of InGaN films remains pseudomorphic to GaN.     

稀土硝酸盐与三缩四乙二醇-二-(8-喹啉基)醚固体配合物的合成

合成了三缩四乙二醇-二-(8-喹啉基)醚(Ⅰ)配体,并首次合成了与十四个稀土硝酸盐的固体配合物.用IR、TG、DTA等测试确定固体配合物组成为[Ln(NO_3)_3]_3(Ⅰ)_2(Ln=La、Ce、Pr、Nd)和CLn(NO_3)_3)_3(Ⅰ)·H_2O(Ln=Sm-Yb和Y).配体(Ⅰ)和配合物[La(NO_3)_3)]_3(Ⅰ)_2核磁共振谱分析表明,醚链上的质子向低场位移,喹啉环上质子向高场位移,这说明镧与配体(Ⅰ)中喹啉上的氮是直接配位的.     

Analysis of localization effect in blue-violet light emitting InGaN/GaN multiple quantum wells with different well widths

Four blue-violet light emitting InGaN/GaN multiple quantum well(MQW) structures with different well widths are grown by metal–organic chemical vapor deposition. The carrier localization effect in these samples is investigated mainly by temperature-dependent photoluminescence measurements. It is found that the localization effect is enhanced as the well width increases from 1.8 nm to 3.6 nm in our experiments. The temperature induced PL peak blueshift and linewidth variation increase with increasing well width, implying that a greater amplitude of potential fluctuation as well as more localization states exist in wider wells. In addition, it is noted that the broadening of the PL spectra always occurs mainly on the low-energy side of the PL spectra due to the temperature-induced band-gap shrinkage, while in the case of the widest well, a large extension of the spectral curve also occurs in the high energy sides due to the existence of more shallow localized centers.     

基于贝叶斯算法的CPU散热片结构自动优化

本文基于数值模拟、结构设计、优化设计以及贝叶斯优化算法提出一种针对散热片结构的自动优化框架,并对CPU正弦式散热片的振幅、周期和高度进行结构优化。结果表明,优化后的正弦式散热片与平板式散热片和初始正弦式散热片相比,表面平均努塞尔数提高了195%,表面最高温度降低了6.51?C。分析了优化前后正弦散热片场协同角的变化,进一步证实了流场和温度场协同性能对散热的本质影响。     

基于Vague集多准则决策的新的评分函数

评分函数是Vague集多准则决策过程中影响决策结果的一个重要因素.针对模糊环境下多准则决策问题,首先,指出现有文献所构造的评分函数的缺陷.其次,在整合前人工作的基础上,为同时兼顾真、假隶属度的绝对差距和未知度对决策结果的贡献,提出了一种新的评分函数,有效地解决了决策结果与直觉判断不符的问题,并在多方案的评分函数值相等时,给出了合理的决策规则,为决策者做出科学决策提供了一种方便有效的方法.最后,通过实例阐明新评分函数的有效性和优越性.     

基于非下采样轮廓波变换遥感影像超分辨重建方法

针对现有非下采样轮廓波变换(NSCT)超分辨率重建方法的不足提出了一种改进的重建方法。空间频率大小反映图像细节信息丰富的程度,改进方法将区域窗口内空间频率的大小作为定权的标准对NSCT分解获得的各对应高频图像进行自适应加权融合。将NSCT分析与自适应加权融合相结合用以实现影像超分辨率重建,其中利用自适应加权融合方法将各高频图像分别进行融合,同时将低频图像进行取均值处理,分别获得处理后的高低频图像,通过NSCT逆变换获得最终的超分辨图像。通过仿真实验与工程应用验证了改进方法的可行性与有效性。     

应用化学镀铜的细导线制造技术

研究出两种应用化学镀铜制造精细电路图形的加成法工艺,并报道了上述加成法的工艺特点,制作加成电路所用的材料及电路的性能。     

含盐二元系的等压气液平衡研究

本文用改进的Rose釜分别测定了在750mmHg压力下的丙酮－甲醇－NaI体系和700mmHg压力下的异丙醇－水－LiCl、CaCl2、NH4Cl、(CH3)4NCl体系的气液平衡数据，当双液系组成固定时，盐的浓度与沸点之间存在线性关系,与热力学导出的线性关系基本相符。     

器件参数对GaN基n~+-GaN/i-Al_x Ga_(1-x)N/n~+-GaN结构紫外和红外双色探测器中紫外响应的影响

研究了AlGaN层参数对GaN基n+-GaN/i-AlxGa1-xN/n+-GaN结构紫外和红外双色探测器中紫外响应的影响规律及物理机制.模拟计算发现:降低AlGaN层本底载流子浓度会增加器件的量子效率,当本底载流子浓度不能进一步降低时,可以通过减小AlGaN层的厚度以保证器件的量子效率.在材料生长和器件工艺过程中都应减少界面态.外加较小的反向偏压能大幅度提高紫外量子效率,分析表明,GaN/AlGaN/GaN形成的两个背靠背、方向相反的异质结电场是出现这些现象的根本原因.在实际器件设计中,应该根据需要调节各结构参数,以保证器件的量子效率.