Effects of p-type GaN thickness on optical properties of GaN-based light-emitting diodes

The influence of p-type Ga N(p Ga N) thickness on the light output power(LOP) and internal quantum efficiency(IQE) of light emitting diode(LED) was studied by experiments and simulations. The LOP of Ga N-based LED increases as the thickness of p Ga N layer decreases from 300 nm to 100 nm, and then decreases as the thickness decreases to 50 nm. The LOP of LED with 100-nm-thick pG a N increases by 30.9% compared with that of the conventional LED with 300-nm-thick p Ga N. The variation trend of IQE is similar to that of LOP as the decrease of Ga N thickness. The simulation results demonstrate that the higher light efficiency of LED with 100-nm-thick p Ga N is ascribed to the improvements of the carrier concentrations and recombination rates.     

基于协同过滤的课程推荐模型*

通过对当前高校学生选课的盲目性的分析,提出了一种基于协同过滤的课程推荐方法。首先对课程进行聚类,构建无缺失的课程评价矩阵,在此基础上根据学生对相似课程的评分预测学生的兴趣爱好,为学生提供个性化的课程推荐。该方法在评分数据极端稀疏的情况下也可以为学生作出准确的课程推荐。最后通过实验验证了该推荐方法的实用性,可以有效地减少学生选课的盲目性。     

高分辨X射线衍射表征氮化镓外延层缺陷密度

利用高分辨X射线衍射方法, 分析了在4H-SiC(0001)面上采用金属有机物化学气相沉积(MOCVD)生长的GaN薄膜的位错。采用对称面衍射和斜对称面衍射等方法研究了晶面倾转角、面内扭转角、晶粒尺寸和晶面弯曲半径等参数, 通过排除仪器、晶粒尺寸及晶面弯曲对摇摆曲线半高宽的影响, 从而获得GaN薄膜的螺位错密度和刃位错密度分别为4.62×10⁷ cm^-2和5.20×10⁹ cm^-2, 总位错密度为5.25×10⁹ cm^-2。     

基于循环经济理念的平顶山市固体废弃物资源化利用研究

随着城市人口的不断增加及工业化、城镇化进程的加快,城市固体废弃物产生量逐年增多,与之相比,现阶段城市固体废弃物处理能力严重滞后。将循环经济理念引入城市固体废弃物的管理,是解决当前资源危机和环境危机问题、实现城市可持续发展的必经之路。对平顶山市固体废弃物处理现状进行分析,并结合国内外实践经验,对平顶山市固体废弃物资源化利用提出了对策和建议。     

论国库集中收付制度

实施国库集中收付制度,是我国财政管理体制改革的重大举措.它对于规范预算执行程序,提高财政资金拨付效率;对于规范财政收支,增加财政收支的透明度;对于提高财政资金的使用效率,增强政府的宏观调控能力;对于加强对财政资金支付的监督,从源头上预防腐败等作用显著.但其在实施过程中也遇到一些问题和阻力,对此需采取以下对策:转变更新观念,提高对国库集中收付工作的认识;制定<国库法>,修订相关法律法规,为国库集中收付制度的实施提供法律保证;加快"金财工程"建设,改善基础设计和技术条件;加强业务培训,提高干部素质;加强部门之间的沟通和协调,提高工作效率.     

自动换罐装置

1 自动换罐装置的作用在饮料行业,如啤酒厂、汽水厂、酒厂等需将液体物料装瓶,在罐装过程中,由于贮料罐有数个,当一罐液体物料灌装完后,要中断灌装工作,用人工拆卸灌装机与贮料罐的管道,接通另一罐物料,才能继续生产,这段时间由于灌装机停止工作,影响了产量。尤其是当物料是啤洒、汽水等含有CO_2的饮料,工艺要求饮料液较为稳定。否则,换罐     

我国高校债务风险防范研究

自1999年以来,我国各大高校通过各种举措不断扩大办学规模,改善办学条件,都不同程度地背负了贷款包袱。在分析债务风险产生的基础上,提出了政府、高校与银行三方防范债务风险的对策。     

成败型产品的可靠性估计

估计成败型产品的可靠性．可以先根据试验子梓用数学方法求出可靠性概率分布密度函数，然后对其积分求出其可靠性置信下限．     

Efficiency improvement of AlGaN-based deep ultraviolet LEDs with gradual Al-composition AlGaN conduction layer

The low internal quantum efficiency (IQE) of AlGaN-based deep ultraviolet light emitting diode (DUV-LED) limits its wider application. The main reasons for low IQE include low carrier concentration, poor carrier location and large defects. The bending of energy band between AlGaN electron blocking layer and conduction layer obstructs transport of holes to multiple quantum wells. In this paper, we propose a gradual Al-composition p-type AlGaN (p-AlGaN) conduction layer to improve the light emitting properties of AlGaN-based DUV-LED. Increased carrier concentration in the active region enhances the effective radiative recombination rate of the LED. Consequently, the IQE of our optimazited DUV-LED is increased by 162% in comparison with conventional DUV-LEDs.