Well-width dependence of the emission linewidth in ZnO/MgZnO quantum wells

Photoluminescence (PL) spectra were measured as a function of well width (L(W)) and temperature in ZnO/Mg(0.1)Zn(0.9)O single quantum wells (QWs) with graded thickness. The emission linewidth (full width at half maximum) was extracted from the emission spectra, and its variation as a function of L(W) was studied. The inhomogeneous linewidth obtained at 5 K was found to decrease with increasing L(W) from 1.8 to 3.3 nm due to the reduced potential variation caused by the L(W) fluctuation. Above 3.3 nm, however, the linewidth became larger with increasing L(W), which was explained by the effect related with defect generation due to strain relaxation and exciton expansion in the QW. For the homogenous linewidth broadening, longitudinal optical (LO) phonon scattering and impurity scattering were taken into account. The LO phonon scattering coefficient Γ(LO) and impurity scattering coefficient Γ(imp) were deduced from the temperature dependence of the linewidth of the PL spectra. Evident reduction of Γ(LO) with decreasing L(W) was observed, which was ascribed to the confinement-induced enhancement of the exciton binding energy. Different from Γ(LO), a monotonic increase in Γ(imp) was observed with decreasing L(W), which was attributed to the enhanced penetration of the exciton wave function into the barrier layers

Fabrication and Characteristics of GaN-based Blue VCSEL

利用金属有机物气相沉积技术(MOCVD)在(0001)蓝宝石衬底上生长了Ga N基垂直腔面发射激光器(VCSEL)的多量子阱腔层结构。X射线衍射测量显示该多量子阱具有良好周期结构和平整界面。运用键合及激光剥离技术将该外延片制作成VCSEL,顶部和底部反射镜为极高反射率的介质膜分布布拉格反射镜(DBR)。在室温、紫外脉冲激光的泵浦条件下,观察到了VCSEL明显的激射现象,峰值波长位于447.7 nm,半高宽为0.11 nm,自发辐射因子约为6.0×10-2,阈值能量密度约为8.8 m J/cm2。在大幅度降低制作难度的情况下,得到目前国际最好结果同样数量级的激射阈值。降低器件制作难度有利于制备的重复性,有利于器件的产品化。Ga N-based multiple quantum wells( MQWs) were epitaxially grown on( 0001)-oriented sapphire substrate by metal organic chemical vapor deposition( MOCVD) technique. X-ray diffraction measurements indicated that the MQWs had good periodic structure and smooth interface. By employing bonding and laser lift-off techniques,the MQW structure was sandwiched between two high reflectivity dielectric distributed Bragg reflectors( DBRs),forming a vertical-cavity surfaceemitting laser( VCSEL). Under optical pumping,the VCSEL achieved laser action at room temperature with a threshold pumping energy density of about 8. 8 m J / cm2. The laser emitted a blue light at 447. 7 nm with a narrow linewidth of 0. 11 nm,and had a high spontaneous emission factor of about 6. 0 × 10- 2.国家自然科学基金(61307115);; 福建省教育厅A类科技项目(JA12249);; 厦门理工学院高校高层次人才基金(YKJ11026R);; 福建省自然科学基金(2013J05104)资助项

Polishing of Laser Lift-off-Induced GaN Surface

激光剥离(llO)技术是研制新型氮化镓(gAn)基谐振腔结构光电子器件的关键技术。然而llO后的gAn表面往往具有较大的粗糙度,而制作谐振腔结构器件需要很高的表面平整度,因此需要对llO后的gAn表面进行抛光。分别采用金刚石粉抛光液和胶粒二氧化硅抛光液进行机械抛光和化学机械抛光(CMP),并对比了两种方法获得的抛光结果,研究发现前者会在抛光后的gAn表面引入划痕,而采用后者可以得到亚纳米级平整度的表面。进一步的实验结果表明,胶粒二氧化硅抛光液同样适用于图形化衬底外延片激光剥离后的gAn表面抛光。Laser lift-off( LLO) is a key technology in development of new GaN-based resonant-cavity optoelectronic devices.For cavity-dependent devices,a smooth surface is highly required.However,the GaN surface after LLO is usually rough,and the polishing is necessary.The mechanical polishing of diamond powder and the chemical mechanical polishing of colloidal silica were compared.It is found that diamond powder leads to scratches on the GaN surface whereas colloidal silica leads to smooth surface with sub-nanometer roughness.The experiment results indicate that polishing with colloidal silica solutions can be applied to smoothen the LLO-produced GaN surface from an epitaxial wafer grown on patterned-sapphire substrate.国家自然科学基金资助项目(61274052;61106044); 中国科学院纳米器件与应用重点实验室开放课题资助项目(14ZS02

Influence of p-GaN Annealing on Optical Properties of InGaN MQWs

近年来,n2退火和O2退火均被用于激活P-gAn中的Mg受主以提高P-gAn中的空穴浓度。基于两种退火技术,系统地研究了n2退火和O2退火对lEd样品电学性能及光学性能的影响。电流电压特性的测试结果显示,在较低温度(500℃)下O2退火就可以达到与n2高温退火(800℃)相似的电学特性。变温光致发光测试表明,n2高温退火会在IngAn量子阱中形成In团簇,In团簇作为深的势阱增加了对载流子的束缚,能够将载流子更好地局限在势阱中。然而In团簇形成的同时也伴随着大量位错的产生,使其IngAn量子阱中的位错密度大幅度提高,因此室温下n2退火样品的辐射复合效率低于O2退火样品的辐射复合效率。In recent years,thermal annealing in either N2 ambient or O2 ambient was used to activate the Mg-doped GaN epilayer and thus improve the density of holes in p-GaN.The electrical and optical properties of LED samples annealed in different ambient were systematically investigated.The test results of I-V characteristics show that samples annealed at low temperature(500 ℃) in O2 ambient and high temperature(800 ℃)in N2 ambient show similar current-voltage characteristics.The temperature-dependent photoluminescence(PL)measurement shows that high-temperature thermal annealing in N2 ambient can induce In clusters in InGaN multiple quantum well(MQWs).The deep traps induced by In clusters can work as localized centers which can enhance the confinement of carriers,the cavriers can be better boanded in well.However,there are much more dislocations out of the trap centers caused by high-temperature annealing,the dislocation density of InGaN MQWs increased significantly.Therefore,at room temperature,the radiative efficiency of the sample annealed in N2 ambient was lower than that annealed in O2 ambient.国家自然科学基金(10974165;91023048;61106044); 高等学校博士学科点专项科研基金(20110121110029

Neurotoxic Effects of Co-exposure to Lead and Dechlorane Plus on Zebrafish (Danio rerio) Embryos

以斑马鱼(Danio rerio)为研究对象,探讨铅(Pb); 、得克隆(DP)及二者联合急性暴露对斑马鱼胚胎的神经毒性作用。结果表明,Pb(5、20 mug·L~(-1))和DP(15、60; mug·L~(-1))单独暴露均会引起斑马鱼自主运动频率增加,触摸反应能力和自由游泳活力下降,并且抑制初级运动神经元的生长,加剧尾部细胞凋亡。但; 与20 mug·L~(-1) Pb单独暴露相比,高剂量联合暴露(20 mug·L~(-1) Pb + 60 mug·L~(-1); DP)使斑马鱼的自主运动频率显著降低(P < 0.05),触摸反应能力和自由游泳活力显著增强(P <; 0.05),初级运动神经元轴突长度显著增加(P < 0.05),尾部细胞凋亡减少。与5 mug·L~(-1); Pb单独暴露相比,低剂量联合暴露(5 mug·L~(-1) Pb + 15 mug·L~(-1) DP)也显著减少斑马鱼尾部的细胞凋亡(P <; 0.05); 。上述结果表明,Pb或DP单独暴露对斑马鱼均可引起神经毒性作用;但二者联合暴露对斑马鱼自主运动、触摸反应以及自由游泳活力的影响则表现为拮抗作用。Neurotoxic effects of acute exposure to lead (Pb) or Dechlorane Plus; (DP),or both were investigated using zebrafish (Danio rerio) embryos.; Results showed that exposure to Pb (5,20 mug·L~(-1)) or DP (15,60 mug·; L-1) alone increased spontaneous movement,decreased touch response and; free-swimming activity,inhibited axonal growth of primary motoneuron and; induced cell apoptosis in zebrafish embryos. Co-exposure to 20; mug·L~(-1) Pb and 60 mug·L~(-1) DP significantly decreased spontaneous; movement (P < 0.05),enhanced touch response and free-swimming activity; (P < 0.05),increased axonal length of primary motoneuron (P < 0.05) and; reduced cell apoptosis in zebrafish when compared to 20 mug·L~(-1) Pb; exposure alone. Co-exposure to 5 mug·L~(-1) Pb and 15 mug·L~(-1) DP also; significantly decreased cell apoptosis on the tail region when compared; to 5 mug·L~(-1) Pb exposure alone (P < 0.05). These results demonstrated; that Pb or DP exposure alone could induce neurobehavioral toxicity in; zebrafish, but Pb and DP co-exposure had antagonistic effects on; spontaneous movements,touch response and free swimming activity.国家自然科学基金项目; 高等学校博士学科点专项科研基

Pollution Characteristics and Ecological Risk of PBDEs in Water and Sediment from an Electronic Waste Dismantling Area in Taizhou

以台州某电子垃圾拆解工业园为圆心,在半径为16 km的范围内,由近及远设计了C(3 km)、S(5~10 km)和R(10~16km)三圈共30个采样点,研究了该区域水及沉积物中多溴联苯醚(PBDEs)的污染特征与生态风险.结果表明,水中PBDEs含量为9.4~57.2 ng·L~(-1),平均值为25.9 ng·L~(-1);沉积物中PBDEs含量为3.7~38 775 ng·g~(-1),平均值为2 779 ng·g~(-1);BDE-209均为主要成分.水及沉积物中PBDEs含量的空间分布态势均为:C圈>S圈>R圈,沉积物中PBDEs含量和离工业园区中心的距离呈极显著负相关(P S > R. Furthermore,the concentrations of PBDEs in sediments showed significant negative correlation against the distance from the industrial park( P < 0. 01). Compared with other regions around the world,the PBDEs contamination was more serious in the area,which indicated that e-waste dismantling activity was one of the significant sources for PBDEs pollution. It was estimated that a total of 30. 7 t PBDEs( including 28. 9 t BDE-209) was discharged into surrounding environment as a result of dismantling industrial activities in last 40 years. A preliminary ecological risk assessment for PBDEs in water and sediments was conducted by hazard quotient method. The results demonstrated that the Penta-BDEs in the center of e-waste dismantling area( a radius of 1. 5 km) was at particularly high risk level and could cause serious influence on the ecological safety and human health.环境保护公益性行业科研专项(201309047

厦门西海域表层水中PAHs污染与PAHs降解菌分布的关系

在厦门西海域设置6个站位,于2001年7月和10月两个航次对各站位表层水中多环芳烃(polycyclicaromatichydrocarbons,PAHs)的含量及几种常见PAHs的降解菌的数量进行调查,结果表明:表层水中PAHs的含量很不稳定,存在明显的时间变化。在7月的调查中,表层水中能检测到的PAHs以2—3环的为主,而在10月以4—6环的为主。低分子量的PAHs—芴和菲的含量与其降解菌的数量之间具有明显的正相关,而高分子量的PAHs—荧蒽和芘的含量与其降解菌的数量之间没有表现出相关性

鲑鳟通用型低通量单核苷酸多态性芯片的开发

为开发常见鲑鳟养殖物种通用的遗传分析工具,本研究利用Affymetrix虹鳟（Oncorhynchus mykiss） 57K高通量单核苷酸多态性（Single nucleotide polymorphism,SNP）芯片,对国内代表性鲑鳟养殖群体开展了分型检测,包括山女鳟（Oncorhynchus masou masou）、银鲑（Oncorhynchus kisutch）、美洲红点鲑（Salvelinus fontinalis）、白斑红点鲑（Salvelinus leucomaenis） 4个物种,从57,501个SNP标记中筛选出96个共享多态性标记,应用Fluigidm 96.96动态芯片平台,构建了大麻哈鱼属（Oncorhynchus）和红点鲑属（Salvelinus）通用型低通量SNP芯片。该芯片分型结果准确性较高,与Affymetrix高通量芯片分型一致性达到96.55%。使用该芯片对来自6个家系的48尾银鲑个体及其候选亲本进行检测,应用Cervus 3.0.7软件进行亲权鉴定,结果能够准确重现复杂家系的真实系谱。在用于单亲本亲权鉴定时,第一亲本非排除率（Non-exclusion probability for first parent, NE-1P）为4.120×10–4;用于双亲本亲权鉴定时,双亲非排除率（Non-exclusion probability for parent pair, NE-PP）低至6.219×10–12,表明该芯片在鲑鳟养殖群体系谱鉴定应用中具有较高的准确性。使用该芯片开展4个鲑鳟养殖群体遗传结构分析,样本分群聚类结果与其所属的分类阶元相符,能够准确反映群体遗传组分构成和遗传关系。本研究构建的低通量SNP芯片在常见鲑鳟养殖物种中具有良好的通用性,将其应用于养殖群体遗传分析,能够为鲑鳟制种、育种和引种等科学决策提供基因组信息参考。国家科技支撑计划项目(2015BAD25B01);;中国水产科学研究院基本科研业务费专项(2015C007)共同资助~

Effect of Laser Pulse Width on the Laser Lift-off Process of GaN Films

Major Research Plan of the National Natural Science Foundation of China [91023048]; National Natural Science Foundation of China [61106044, 10974165]; Doctoral Program Foundation of Institutions of Higher Education of China [20110121110029]Laser lift-off (LLO), by which GaN is separated from sapphire, is demonstrated to be a promising technique for advanced GaN-based optoelectronic devices. Its physical insight, however, is still not fully understood. We study systematically the effect of laser pulse width on the LLO process and the property of GaN. To estimate accurately the temperature distribution and the decomposed thickness of GaN, fluctuation in the pulse laser energy is taken into account. It is found that the temperature at the interface is increased in a higher speed for a narrower pulse width. In addition, less damage to the GaN film is expected for a narrower pulse width owing to the smaller heated area, lower transient temperature and lower N-2 vapor pressure encountered during LLO. Some experimental results reported in literature are explained well. Our results are useful in understanding the effect of laser pulse width and can be taken as references in LLO of GaN/sapphire structures

MOCVD growth of high-reflectivity AlN/GaN distributed Bragg reflectors

利用金属有机物化学气相沉积(MOCVD)方法在蓝宝石c面衬底上制备出高反射率AlN/GaN分布布拉格反射镜(DBR)。利用分光光度计测量,在418 nm附近最大反射率达到99%。样品表面显微照片显示,有圆弧形缺陷和少量裂纹出现;在缺陷和裂纹以外的区域,DBR具有较为平坦的表面,其粗糙度在10μm×10μm面积上为3.3 nm左右。样品的截面扫描电镜(SEM)照片显示,DBR具有良好的周期性。对反射率和表面分析的结果表明,该样品达到了制备GaN基垂直腔面发射激光器(VCSEL)的要求。A high reflectivity AlN/GaN distributed Bragg reflector(DBR) is grown on c-plane sapphire substrate by metalorganic chemical vapor deposition(MOCVD).A peak reflectivity of 99% is observed around 418 nm by spectrophotometer.Compass-shape defects and a few cracks are observed on the surface.The surface root mean square(RMS) of roughness in the flat area is around 3.3 nm over a 10 μm×10 μm area.The cross-sectional scanning electron microscope(SEM) image reveals the good periodicity of DBR.Considering the peak reflectivity and surface morphology,the DBR can be used to fabricate GaN-based vertical cavity surface emitting laser(VCSEL).国家高技术研究“863”计划资助项目(2006AA03Z409