Room-Temperature Continuous-Wave Operation of InGaN-Based Blue-Violet Laser Diodes with a Lifetime of 15.6 Hours

We report our recent progress of investigations on InGaN-based blue-violet laser diodes （LDs）. The roomtemperature （RT） cw operation lifetime of LDs has extended to longer than 15.6 h. The LD structure was grown on a c-plane free-standing （FS） GaN substrate by metal organic chemical vapor deposition （MOCVD）. The typical threshold current and voltage of LD under RT cw operation are 78 mA and 6.8 V, respectively. The experimental analysis of degradation of LD performances suggests that after aging treatment, the increase of series resistance and threshold current can be mainly attributed to the deterioration of p-type ohmic contact and the decrease of internal quantum efticiency of multiple quantum well （MQW）, respectively.     

Fabrication and Characterization of High Power InGaN Blue-Violet Lasers with an Array Structure

InGaN/GaN multi-quantum-well-structure laser diodes with an array structure are successfully fabricated on sapphire substrates. The laser diode consists of four emitter stripes which share common electrodes on one laser chip. An 800-μm-long cavity is formed by cleaving the substrate along the （1100） orientation using laser scriber. The threshold current and voltage of the laser array diode are 2A and 10.5 V, respectively. A light output peak power of 12 W under pulsed current injection at room temperature is achieved. We simulate the electric properties of GaN based laser diode in a co-planar structure and the results show that minimizing the difference of distances between the different ridges and the n-electrode and increasing the electrical conductivity of the n-type GaN are two effective ways to improve the uniformity of carrier distribution in emitter stripes. Two pairs of emitters on a chip are arranged to be located near the two n-electrode pads on the left and right sides, and the four stripe emitters can laser together. The laser diode shows two sharp peaks of light output at 408 and 409 nm above the threshold current. The full widths at half maximum for the parallel and perpendicular far field patterns are 8° and 32°, respectively.     

纳米折叠InGaN/GaN LED材料生长及器件特性

在以自组织Ni纳米岛为掩膜制作的n-GaN纳米柱上,利用MOCVD方法外延生长了具有折叠InGaN/GaN多量子阱(MQW)的LED结构外延片,进而制作了LED器件.外延片上中下游的光致荧光测试,结果表明外延片具有很好的均匀性.用该外延片制作的LED的电致发光谱,随注入电流增加没有明显蓝移,这表明纳米结构能更好地释放应力,纳米柱上外延生长的多量子阱,具有较低的压电极化电场.正向工作电流20 mA时,LED器件的工作电压为4.6 V. 关键词： 纳米柱LED 光致发光 电致发光     

固体催化剂活性表面的化学不均匀性

固体催化剂活性表面的化学不均匀性朱建军林西平＊（江苏石油化工学院化学工程系常州２１３０１６）关键词固体催化剂，活性表面，分形维，化学不均匀性１９９６－１０－２８收稿，１９９７－０３－１０修回中国石化总公司和回国留学服务中心资助项目本院九五届毕业生于晓...     

液液相变中的盐效应

完全互溶的双液系在一定条件下发生相变而成为部分互溶体系.六十年代,李俊甫等曾研究过盐的加入对相变条件的影响,提出了线性方程:T=T_0+Kx_x。(T_0,T分别为双液比固定时加盐前后体系的相变温度,x_s为盐的摩尔分数,K为常数).但至今尚无人从理论上证明其存在并加以计算.本文试从微扰理论出发证明该线性方程成立,并对部分体系进行计算。     

考虑双参照点和Choquet积分的新型研发机构绩效评估方法及应用

针对新型研发机构绩效评估值不确定、指标间存在关联、投资主体多元且有风险偏好、指标集权重未知等绩效问题,提出基于双参照点和Choquet积分的绩效评估方法。首先,结合新型研发机构的特点,构建绩效评估指标体系;其次,基于累积前景理论设计同行-期望双参照点;然后,构建指标间直接关联矩阵,依据K-可加模糊测度和平均边际贡献Banzhaf值优化求解指标集权重,代入Choquet积分方法和参照点权重公式计算各新型研发机构的综合绩效评估值,从而实现机构排序和问题分析。该方法考虑了新型研发机构的特点、数据不确定性、指标关联性、风险偏好性、权重未知性等因素,更加符合实际情况,案例验证了方法的有效性和实用性。     

GaN横向外延中晶面倾斜的形成机制

采用双晶X射线衍射(DC-XRD)研究蓝宝石(0001)衬底上横向外延GaN层中晶面倾斜的形成原因. 发现横向生长区的GaN在垂直掩模方向上朝SiN_x掩模层弯曲. 采用选择性腐蚀逐渐去掉SiN_x掩模层, 发现XRD中GaN(0002)w扫描衍射峰两侧存在与晶面倾斜有关的衍射信息. 该衍射信息起初为一个很宽的峰, 随着选择性腐蚀的进行, 会先分裂为两个峰, 最后当SiN_x掩模层全部腐蚀掉后, 其中一个衍射峰会消失, 而只剩下一个很窄的峰. 作者证实造成横向外延GaN 中晶面倾斜的原因有两个: 一是由于GaN与掩模层之间界面应力造成的弹性非均匀应变; 另一个是由于GaN中穿透位错的90°转向造成的塑性形变.     

稀土硫氰酸盐与聚乙二醇固体配合物的合成与表征

在乙酸乙酯溶液中合成了十五种稀土硫氰酸盐与开环聚醚,三缩四乙二醇(简写EO4)的固体配合物.用元素分析,红外光谱,差热和热重分析,核磁共振,X射线粉末衍射及摩尔电导等方法对配合物进行了表征.配合物的组成为RE(SCN)_3·EO_4·H_2O.从TG-DTA分析表明,除镧的配合物外其他配合物在160℃—260℃能生成RE:EO_4为4:3的新配合物.     

Metal-semiconductor-metal ultraviolet photodetector based on GaN

A metal-semiconductor-metal (MSM) ultraviolet photodetector has been fabricated using unintentionally doped n-GaN films grown on sapphire substrates. Its dark current, photocurrent under the illumination with λ = 360 nm light, responsivity, and the dependence of responsivity on bias voltage were measured at room temperature. The dark current of the photodetector is 1.03 Na under 5 V bias, and is 15.3 Na under 10 V bias. A maximum responsivity of 0.166 A/W has been achieved under the illumination with λ= 366 nm light and 15 V bias. It exhibits a typical sharp band-edge cutoff at the wavelength of 366 nm, and a high responsivity at the wavelength from 320 nm to 366 nm. Its responsivity under the illumination with λ= 360 nm light increases when the bias voltage increases.     

M/V-Al-2O3型催化剂的制备、表征及催化性能研究

采用等体积浸渍法制备了M/γ-Al2O3系列催化剂,M为NaOH、KOH、MgO,通过XRD、BET等测试技术对催化剂进行了表征,并将催化剂应用于二乙醇胺催化脱水制备吗啉反应中,实验考察了修饰剂及负载量、反应温度、压力等对催化剂活性的影响。结果表明,NaOH/γ-Al2O3、KOH/γ-Al2O3、MgO/γ-Al2O3催化剂具有高的催化活性及对吗啉制备的高选择性,其原因是此反应需要中强酸及弱酸中心,强酸中心易使催化剂表面积炭,经过NaOH、KOH、Mg(OH)2修饰的γ-Al2O3其强酸中心减少而中强酸和弱酸中心相应增加,从而提高了催化剂的活性、选择性和稳定性。