Improvement of characteristics of an InGaN light-emitting diode by using a staggered AlGaN electron-blocking layer

The optical and physical properties of an InGaN light-emitting diode (LED) with a specific design of a staggered AlGaN electron-blocking layer (EBL) are investigated numerically in detail. The electrostatic field distribution, energy band, carrier concentration, electroluminescence (EL) intensity, internal quantum efficiency (IQE), and the output power are simulated. The results reveal that this specific design has a remarkable improvement in optical performance compared with the design of a conventional LED. The lower electron leakage current, higher hole injection efficiency, and consequently mitigated efficiency droop are achieved. The significant decrease of electrostatic field at the interface between the last barrier and the EBL of the LED could be one of the main reasons for these improvements.     

非相对论弱相互作用玻色气体的有效场理论处理

采用有效场理论研究了非相对论弱相互作用玻色-爱因斯坦凝聚量子气体的一般性质.在分析了系统的不可重整化性质后,从有效拉氏量出发,计算了最低阶环路修正下拉氏量参量的运动耦合常数(running coupling constant)的形式,并且得到了相应的微分方程.研究结果表明,不同于相对论玻色气体的有效理论,对非相对论弱相互作用的玻色气体,可以移除该有效理论中的内禀能量尺度,即可令该有效理论的内禀能量尺度取无穷大值.所得的分析结果将有助于对玻色-爱因斯坦凝聚的临界性质和行为的深入研究.     

(CdZnTe,ZnS)/ZnTe复合量子阱的光学特性研究

设计并制备了一种新型的(CdZnTe,ZnS)/ZnTe复合量子阱结构.使CdZnTe量子阱中的激子有可能在短时间内隧穿到ZnS阱层,从而达到提高光双稳器件“关”速度的目的.并通过对发光特性的研究证实在我们设计的结构中横向激子隧穿的存在,从而为进一步研究超高速光开关提供了实验依据.     

便携式无线人体脂肪率测量仪的设计

生物电阻抗法(BIA)是一种安全非侵入式的、结果可靠有效的人体组成成分(脂肪含量)测量方法。以此为原理,设计了一款便携式无线人体脂肪率测量仪。硬件上,系统以高集成化、低功耗的阻抗测量芯片AD5933为核心,通过蓝牙实现与上位机的无线通信,大大降低了设备的复杂度。软件部分提出一种单频点小阻抗范围的增益系数校准方式,计算量小且容易实现。将新测量仪和欧姆龙体脂仪HBF-358进行对比实验,并作Bland-Altman一致性分析。结果表明,二者的相关系数为0.997。此外,该测量仪还具有易操作、小型化的特点。     

The relation between the generalised Eshelby integral and the generalised BCS and DB modelsvspace1mm

The generalised BCS dislocation group model and the generalised DB atomic cohesive force zone model have obtained the same results on nonlinear fracture study of some one-, two- and three-dimensional quasicrystals. This work reveals some inherent connection between the two models, and finds that their common basis is the generalised Eshelby integral based on the generalised Eshelby energy--momentum tensor for quasicrystals. Further applications of the theory in solving nonlinear fracture problems of the materials are also discussed.     

介质阻挡放电跃变升压模式下靶波斑图研究

在大气压氩气介质阻挡放电中,首次通过跃变外加电压得到了稳定的靶波斑图.实验分别研究了跃变再缓变和直接跃变升压模式下靶波斑图的稳定性和波长选择.研究发现,跃变再缓变升压之后得到的靶波斑图不稳定,其与螺旋波相互转换.在这种转换中,靶波每次出现的时间为几十毫秒.直接跃变升压得到的靶波斑图稳定性明显增强,其稳定时间通常为5 min以上.比较不同升压模式下靶波斑图的波长,发现直接跃变升压模式下波长随电压升高减小较快.综上表明,升压模式对靶波斑图的稳定性和波长都有影响. 关键词： 介质阻挡放电 靶波斑图 跃变升压 缓变升压     

(Mg(BH_4)_2)_n团簇结构与性质的密度泛函理论研究

采用了密度泛函理论中的杂化密度泛函B3LYP方法,在6-31G*基组水平上对[Mg(BH_4)_2]_n(n=1-3)团簇的结构进行了优化,几何结构优化时自旋多重度取了1、3、5等多种情况进行计算.最后对最稳定结构的振动特性、成键特性、电荷特性和稳定性等进行了研究.结论表明:团簇最稳定结构易形成链状结构,其中Mg-B键长为0.210～0.253 nm,-BH_4基中靠近Mg原子处的B-H键长约为0.125 nm、远离Mg原子处的B-H键长为0.119 nm.对比团簇和晶体的光谱结构表明,-BH_4基在团簇和晶体中结构基本一致. Mg原子的自然电荷在1.687～1.757e之间,B原子的自然电荷在-0.702～-0.788e之间,H原子基本不参与电荷转移,其自然电荷在-0.094～0.070e之间.团簇中Mg原子和-BH_4基之间相互作用呈现较强的离子性,Mg(BH_4)_2团簇具有相对较高的动力学稳定性.     

可变色的ZnSe:Er3+ MIS发光二极管

本文首次利用高场和低场激发下的有效发光中心,设计和制备了随外加电压极性改变而变色的ZoSe:Er3+ MIS发光二极管。这种发光二极管在正向电压激发下得到蓝色发光,而在反向电压激发下得到绿色发光。     

High-voltage SOI lateral MOSFET with a dual vertical field plate

A new silicon-on-insulator(SOI)power lateral MOSFET with a dual vertical field plate(VFP)in the oxide trench is proposed.The dual VFP modulates the distribution of the electric field in the drift region,which enhances the internal field of the drift region and increases the drift doping concentration of the drift region,resulting in remarkable improvements in breakdown voltage(BV)and specific on-resistance(Ron,sp).The mechanism of the VFP is analyzed and the characteristics of BV and Ron,spare discussed.It is shown that the BV of the proposed device increases from 389 V of the conventional device to 589 V,and the Ron,sp decreases from 366 m·cm2to 110 m·cm2.     

Defect-induced failure of optical coating filters

Optical filters composed of Ag, Al₂O₃, and ZnSe films were prepared on BK7 substrates by evaporation. By employing spectrophotometer, microscope, scanning electron microscope (SEM), and energy dispersive spectrum (EDS) analysis, the moisture-dependent stability of the samples was tested. The experimental results revealed that filter failure often occurs initially at defect sites. Small sputtering particles and pinhole are found to be two types of defects that induced the optical coating filter failure. The mechanisms of the defect-induced failure of the filters also are discussed in the article.