Influences of polarization effect and p-region doping concentration on the photocurrent response of solar-blind p–i–n avalanche photodiodes

The influences of polarization and p-region doping concentration on the photocurrent response of Al0.4Ga0.6N/Al0.4Ga0.6N/Al0.65Ga0.35N p–i–n avalanche photodetector are studied in a wide range of reverse bias voltages.The simulation results indicate that the photocurrent under high inverse bias voltage decreases with the increase of polarization effect,but increases rapidly with the increase of effective doping concentration in p-type region.These phenomena are analyzed based on the calculations of the intensity and distribution of the electric field.A high p-region doping concentration in the p–i–n avalanche photodetector is shown to be important for the efficient compensation for the detrimental polarization-induced electrostatic field.     

一类新型绝对接近关联度分析模型及应用

定义了一种新的灰色接近关联度模型—绝对接近关联度。研究了现有接近关联度的性质及问题,进而提出了新型绝对接近关联度的定义;研究了绝对接近关联度的计算方法;探讨了绝对接近关联度所具有的若干性质;将绝对接近关联度模型用于基于三角模糊数的多属性决策中,算例说明了方法的应用步骤和可行性。     

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.     

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.     

考虑双参照点累积前景理论的风险型群决策方法

针对决策者权重信息、属性值为区间数形式的风险型多属性群决策问题,提出了一种考虑双参照点累积前景理论的群决策方法。考虑预期和正理想点为双参照点,根据累积前景理论分别表示针对双参照点的价值;引入预期侧重系数,进一步得到各方案的加权累积前景值;根据离差最大化的思想建立决策者权重优化模型,据此计算各方案综合累积前景值并进行方案排序。最后运用到工程评标案例中,通过与单参照点、期望效用理论的比较验证了该方法的有效性和实用性。     

Pt/Al2O3和Pt-Cu/Al2O3催化CCl4氢化脱氯反应

制备了Al2O3负载Pt单金属催化剂和负载Pt-Cu双金属催化剂,比较了二者不同还原温度对其催化CCl4氢化脱氯反应性能的影响。 单金属Pt催化剂上主要生成CHCl3,而双金属Pt-Cu催化剂上产物随催化剂制备时的还原温度不同而异,当催化剂经400 ℃用H2还原后产物主要为CHCl3,而当催化剂经800 ℃用H2还原后产物主要为CCl2CCl2。 由于CCl4氢化反应是强放热反应,催化剂表面局部过热使得在反应中生成的C2等产物聚合结焦,覆盖了催化剂的活性中心,导致催化剂失活。 因此,通过加入甲醇作为稀释剂以带走部分反应热可提高催化剂的稳定性。 同时也降低了CHCl3的选择性,提高了CCl2CCl2的选择性。     

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.     

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。     

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。