Investigation of GaN-based Resonant Cavity Light Emitting Devices

GaN基宽禁带半导体材料具有优异的物理和化学特性，其合金材料的禁带宽度在0.7-6.2eV之间连续可调，对应的光波长覆盖红外-可见-紫外光范围且任一组分的合金均为直接带隙，已被广泛应用于制作高效率半导体发光器件。尤其是蓝绿光波段的发光器件，是国际研究的热点，其结构和性能不断得到优化和提高。设计和制作新型结构的发光器件是提高器件性能的一种有效途径。本论文围绕GaN基谐振腔发光器件的研制，在结构设计、材料生长、器件制作、性能测试等多方面进行了细致深入的研究工作，主要内容和成果如下： 1）通过计算和分析谐振腔结构中DBR反射特性和光渗透深度，光场的驻波分布及器件的工作特性包括谐振模式、品质因子、自...GaN-based wide-band gap semiconductors are being widely studied due to their outstanding physical and chemical properties. GaN and its ternary alloys have tunable energy band gaps, which cover the whole visible spectral region. Furthermore, nitride semiconductors are all direct band gap semiconductors, which have great potential for light emission devices especially for the blue and green lights. ...学位：工学博士院系专业：物理与机电工程学院物理学系_微电子学与固体电子学学号：1982008015051

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

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

大鼠移植心心电图改变与急性排斥相关关系

【目的】观察体表心电图指标与移植心脏心肌排斥病理改变和主要组织相容性(MHC)Ⅱ 类抗原表达的相关程 度, 探讨其监测术后急性排斥的可能性。【方法】建立大鼠颈部心脏移植模型, 记录心电图, 同时摘取供心检测排斥病理改变 和MHCⅡ 类抗原表达。【结果】QT 间期和R-R 间期标准差随着心肌急性排斥病变的加重而逐渐增加, 同时与心肌急性排斥病 变和MHCⅡ 类抗原表达相关, QRS 电压降低和R-R 间期的改变并不显著。【结论】心电图QT 间期和R-R 间期标准差也许可 用于心脏移植术后监测急性排斥, 为选择心内膜心肌活检时间提供参考

Development and Output Characteristics of 785 nm Portable Grating-Coupled External Cavity Tunable Semiconductor Laser

针对移频激发拉曼光谱测试系统的小型化需求,在Littrow结构中,采用商用的785; nm大功率激光二极管作为增益器件,构建了一款便携式光栅外腔可调谐半导体激光器。该激光器通过采用一种新型的波长调谐方法,即以改变半导体增益器件相对; 于准直透镜的水平位置来实现波长的连续调谐,实现了尺寸为140 mmX65 mmX50; mm的小型化结构设计。相比于传统的旋转衍射光栅改变光线在光栅上的入射角来实现波长调谐的方式,该方法有效地缩减了增益器件的平移距离,从而有利于便携; 式外腔激光器波长的快速宽带调谐。实验结果表明,该激光器具有较宽的波长调谐范围,在340~900 mA注入电流下均可实现10; nm以上的波长调谐,尤其在900 mA大注入电流下,其波长调谐覆盖779.40~791.07 nm,调谐范围可达11.67; nm,且激射线宽小于0.2 nm,单波长输出功率最高可达mW,放大的自发辐射抑制比大于25; dB,呈现出较优异的输出性能,满足移频激发拉曼光谱检测系统对光源的基本要求。此外,该激光器可采用一微型压电陶瓷驱动器来实现波长的电动调谐,实验获; 得了1.35 nm的波长调谐范围,证实了所制785; nm便携式光栅外腔可调谐半导体激光器适合作为便携式移频激发拉曼光谱检测系统的光源用于减除原始拉曼光谱中的荧光背景。Aiming at the miniaturization requirement of shifted excitation Raman spectroscopy test system, a portable grating-coupled external cavity (EC) tunable semiconductor laser in Littrow configuration is designed and fabricated with a commercial 785 nm high-power laser diode as the gain device. By using a new wavelength tuning method, aiming to change the position of gain device relative to the collimating lens in the horizontal direction, a miniaturized device with the size of 140 mmX 65 mmX 50 mm is designed. Compared to the traditional wavelength tuning method which is to change the light incident angle by rotating the diffraction grating, this new tuning method reduces the translational distance of semiconductor gain device effectively, thus it is conductive to the fast and broad wavelength tuning of portable EC laser. The experimental results show that the EC laser has a wide wavelength tuning range. Under any injection current from 340 to 900 mA, a wavelength tuning range of more than 10 nm can be realized. Especially at 900 mA, good performance including a 11. 67 nm-wavelength tuning range from 779. 40 to 791. 07 nm, a less than 0. 2 nm-spectral linewidth, an up to 280 mW-output power, and a more than 25 dB-amplified spontaneous emission suppression ratio is presented, which fully meets the basic testing requirements of shifted excitation Raman spectroscopy. Moreover, 1. 35 nm-electric wavelength tuning range is achieved by applying a mini-piezoelectric actuator. This indicates that the home-made 785 nm portable grating-coupled EC tunable semiconductor laser is suitable as the light source of portable shifted excitation Raman spectroscopy testing system to eliminate the fluorescence background of Raman spectrum.国家自然科学基金项目（61306087,21303143,61574119）; 福建省自然科学基金计划项目（2013J05096）资

Fabrication of GaN-based Vertical Cavity Surface Emitting Lasers

作者在我国大陆首次实现了GaN基垂直腔面发射激光器(VCSEL)的激射.首先采用金属有机物化学气相沉积(MOCVD)技术在蓝宝石衬底上进行高质量氮化物增益区的外延生长,然后在表面沉积高反射介质膜分布布拉格反射镜(DBR).将样品键合到其它支撑片上后,采用激光剥离技术将蓝宝石衬底去除.再在去除蓝宝石后露出的氮化物表面沉积第二组介质膜DBR制成VCSEL.在室温光泵条件下,观察到VCSEL的激射,激射波长449.5 nm,阈值6.5 mJ/cm2,激射峰的半高宽小于0.1 nm,这些指标达到了国际领先水平.本文为进一步研制实用化氮化物VCSEL奠定了重要的基础.GaN-based vertical surface emitting lasers(VCSELs) have potential applications in various fields such as high-density optical storage.This paper is the first report in mainland of China on lasing action of GaN-based VCSEL.High-quality nitride active gain region was grown on an Al2O3 sapphire substrate using metalorganic chemical vapor deposition(MOCVD).Then a high-reflectivity dielectric distributed Bragg reflector(DBR) was deposited on the surface.After bonding a supporting plate on the surface,the sapphire substrate was removed by a laser-lift-off method and the second dielectric DBR was deposited on the exposed GaN surface to form a VCSEL structure.Lasing action was confirmed under optical pumping at room temperature.The lasing wavelength,threshold and linewidth were 449.5 nm,6.5 mJ/cm2 and 0.1 nm,respectively.The threshold and linewidth are better than those ever reported.The result of this work laid important foundation of current-injected VCSEL based on nitride semiconductors.科技部国家高科技研究发展计划(863计划)资

GaN基垂直腔面发射激光器的研制

作者在我国大陆首次实现了GaN基垂直腔面发射激光器（VCSEL）的激射．首先采用金属有机物化学气相沉积（MOCVD）技术在蓝宝石衬底上进行高质量氮化物增益区的外延生长．然后在表面沉积高反射介质膜分布布拉格反射镜（DBR）．将样品键合到其它支撑片上后，采用激光剥离技术将蓝宝石衬底去除．再在去除蓝宝石后露出的氮化物表面沉积第二组介质膜DBR制成VCSEL．在室温光泵条件下，观察到VCSEL的激射．激射波长449．5nm。阈值6．5mJ／cm~2．激射峰的半高宽小于0．1nm，这些指标达到了国际领先水平．本文为进一步研制实用化氮化物VCSEL奠定了重要的基础