Photoluminescence and microstructure of the Erbium-Doped hydrogenated amorphous SiOx(0 < x < 2)

The hydrogenated amorphous SiOx films (a-SiOx:H) with various oxygen contents have been prepared using plasma enhanced chemical vapor deposition technique. The films were implanted with erbium and annealed by rapid thermal annealing. An intense photoluminescence (PL) of Er at 1.54 mum has been observed at 77 K and at room temperature. The PL intensity depends strongly on both the oxygen content of the film and the rapid thermal annealing temperature and reaches its maximum if the ratio of O/Si in the film is approximately equal to 1.0 at 77 K and to 1.76 at room temperature. The microstructure of the film also has strong influences on the PL intensity. The PL intensity at 250 K is slightly more than a half of that at 15 K. It means that the temperature quenching effect of the PL intensity is very weak.

1.5 mu m luminescence characteristic of erbium in B, P doped a-SiO : H films

Hydrogenated amorphous silicon films co-doped with oxygen (O), boron (B) and phosphorus (P) were fabricated using PECVD technique. The erbium (Er) implanted samples were annealed in a N-2 ambient by rapid thermal annealing. Strong photoluminescence (PL) spectra of these samples were observed at room temperature. The incorporation of O, B and P could not only enhance the PL intensity but also the thermal annealing temperature of the strongest PL intensity. It seems that the incorporation of B or P can decrease the grain boundary potential barriers thus leading to an easier movement of carriers and a stronger PL intensity. Temperature dependence of PL indicated the thermal quenching of Er-doped hydrogenated amorphous silicon is very weak.

Photoluminescence of erbium-doped hydrogenated amorphous SiOx(0 < x < 2)

Hydrogenated amorphous SiOx films are fabricated via plasma enhanced chemical vapor deposition technique. After erbium implantation and rapid thermal annealing, photoluminescence (PL) are measured at 77 K and room temperature (RT), respectively. We observed the strong PL at 1.54 mu m at RT. The 1.54 mu m PL intensity changes with the variation of concentration of oxygen. The most intense PL at 77 K in a-SiOx:H (Er) corresponds to O/Si = 1.0 and at RT to O/Si = 1.76. Based on our results, we propose that Er ions contributed to PL come from O-rich region in the film. Er ions in Si-rich region have no relation with FL. Temperature dependence of the intensity of the 1.54 mu m line of the Er3+ transition displays a very weak temperature quenching in Er-doped hydrogenated amorphous Si. The PL intensity at 250 K is a little more one half of that at 15 K.

Studies of high DC current induced degradation in III-V nitride based heterojunctions

We report experiments on high de current stressing in commercial III-V nitride based heterojunction light-emitting diodes. Stressing currents ranging from 100 mA to 200 mA were used. Degradations in the device properties were investigated through detailed studies of the current-voltage (I-V) characteristics, electroluminescence, deep-level transient Fourier spectroscopy and flicker noise. Our experimental data demonstrated significant distortions in the I-V characteristics subsequent to electrical stressing. The room temperature electro-luminescence of the devices exhibited a 25% decrement in the peak emission intensity. Concentration of the deep-levels was examined by deep-level transient Fourier spectroscopy, which indicated an increase in the density of deep-traps from 2.7 x 10(13) cm(-3) to 4.2 x 10(13) cm(-3) at E-1 = E-C - 1.1 eV. The result is consistent with our study of 1/f noise, which exhibited up to three orders of magnitude increase in the voltage noise power spectra. These traps are typically located at energy levels beyond the range that can be characterized by conventional techniques including DLTS. The two experiments, therefore, provide a more complete picture of trap generation due to high dc current stressing.

Mechanism on exciton-mediated energy transfer in erbium-doped silicon

Exciton-mediated energy transfer model in Er-doped silicon was presented. The emission intensity is related to optically active Er concentration, lifetime of excited Er3+ ion and spontaneous emission. The thermal quenching of the Er luminescence in Si is caused by thermal ionization of Er-bound exciton complex and nonradiative energy back-transfer processes, which correspond to the activation energy of 6.6 and 47.4 meV, respectively. Er doping in silicon introduces donor states, a large enhancement in the electrical activation of Er (up to two orders of magnitude) is obtained by co-implanting Er with O. It appears that the donor states are the gateway to the optically active Er. (C) 2000 Elsevier Science B.V. All rights reserved.

Characterization of hot-electron effects on flicker noise in III-V nitride based heterojunctions

We report experiments on hot-electron stressing in commercial III-V nitride based heterojunction fight-emitting diodes. Stressing currents ranging from 100 mA to 200 mA were used. Degradations in the device properties were investigated through detailed studies of the I-V characteristics, electroluminescence, Deep-Level Transient Fourier Spectroscopy and flicker noise. Our experimental data demonstrated significant distortions in the I-V characteristics. The room temperature electroluminescence of the devices exhibited 25% decrement in the peak emission intensity. Concentration of the deep-levels was examined by measuring the Deep-Level Transient Fourier Spectroscopy, which indicated an increase in the density of deep-traps from 2.7 x 10(13) cm(-3) to 4.21 x 10(13) cm(-3) at E-1 = E-C - 1.1eV. The result is consistent with our study of 1/f noise, which exhibited up to three orders of magnitude increase in the voltage noise power spectra. Our experiments show large increase in both the interface traps and deep-levels resulted from hot-carrier stressing.

Defect influence on luminescence efficiency of GaN-based LEDs

Wafers with normal light-emitting diode structure were grown by metal organic chemical vapor deposition system. The pressure and temperature were varied during growth of buffer layer in order to grow different types of epilayers. The cathodoluminescence results show that the interface distortion of quantum well plays an important role in radiant efficiency. The electroluminescence detections indicate that the dislocations also influence the external quantum efficiency by lowering the electron injection efficiency. (c) 2006 Elsevier Ltd. All rights reserved.

铕铽铝配合物及吡唑啉衍生物的电致发光研究

有机电致发光器件（organiclight-emittingdiodes,OLEDs）由于具有全色、低压直流驱动、视角广、高效率、发光颜色丰富等优点,在平板大面积显示领域具有广阔的应用前景,已引起广泛的重视.至目前为止,各式各样多层结构的器件、新的电致发光功能材料在深入研究,各种发光颜色甚至全色器件都已经相继报道.探索新材料,优化器件结构是目前电致发光研究的主要课题.该文主要包括以下几方面工作：（1）稀土配合物真空蒸镀所成膜的形态结构;（2）稀土配合物中第二配体的引入对稀土配合物电致发光性能的影响;（3）稀土配合物溶解性的改善;（4）铝配合物与聚合物PVK基激复合物对电致发光器件性能的影响及基激复合物的证实;（5）高效吡唑啉生物的合成及其电致发光器件的设计.通过深入系统的研究,取得了创新性的结果.

新型稀土配合物的合成及其光致发光与电致发光性能的研究

稀土配合物作为电致发光材料，具有色纯度高、发光效率高等优点，其作为有机电致发光材料（OLED）具有广阔的应用前景。目前，有关其电致发光（OLED）的研究取得了很大的进展，但将其作为OLED材料达到实用化，还需要很大一段距离。因此，有必要进一步地开发新型、高效、接近实用的稀土配合物并将其应用于OLED的制备中，开发出实用的OLED显示屏。本论文的工作中，将共扼适度的蔡环和多氟取代的烷基链引入到β-二酮配体中，合成了含三氟甲基、五氟乙基、七氟丙基和十五氟庚基的β-二酮配体（TFNB、PFNP、HFNH和PFND），并合成了DPPZ，以及其它配体biPy、phen，用这些配体合成了多种稀土配合物。运用多种手段研究了配合物的晶体结构、热稳定性、光致发光（PL）和电致发光（EL）性质，初步探讨了PL和EL发光机理。合成了四种稀土Eu配合物，它们的PL均表现为Eu3＋的特征发光，其荧光效率的大小顺序为：七氟＞五氟＞十五氟＞三氟。以这四种配合物为发光中心组装了掺杂类型的器件。器件性能表明：五氟配合物和七氟配合物具有最佳结构的器件在其所有驱动电压和电流密度下都可以得到纯的EL光谱（Eu3＋的特征发光）。七氟和五氟配合物的最大亮度都超过了1000cd/m2，效率分别达到了4.14 cd／A和5.41cd/A，流明效率分别为2.28和3.11m/W，这样的高效率，达到和超过了国际上报道的同类型器件的EL性能。我们综合比较了几种配合物的性能，得出了一定的结论，并总结出一些规律来指导材料的合成。合成了Sm的三氟、七氟配合物，利用吸收光谱、荧光光谱初步研究了它们的PL性能，并研究了七氟Sm配合物的EL性能。合成了三氟Pr和七氟Pr、Nd、Er和Yb的配合物，研究了它们的近红外发光性能。通过各种光谱的研究，表明在这些配合物的发光过程中，与可见发光的Eu、Sm配合物一样，“天线效应”起到了很大的作用，因此这些配合物均有较强的近红外发光（800-1700nm）。将咔哇基团引入狡酸中一得到Eu、Tb的配合物，它们具有很强的PL性能。

RECRYSTALLIZATION, IMPURITY MIGRATION AND OPTICAL ACTIVATION OF YB-IMPLANTED SILICON INDUCED BY RAPID THERMAL ANNEALING

The rapid thermal annealing temperature dependence of the recrystallization, Yb migration and its optical activation were studied for Yb-implanted silicon. For the annealing regime 800-1000-degrees-C, the Yb segregates both at the crystal/amorphous interface and at the surface, which is different from the usual segregation of Er at the crystal/amorphous interface, and the efficiency of optical activation also increases with annealing temperature. However, the amorphous layer regrows completely and no photoluminescence is observed after the annealing at 1200-degrees-C.

Electro-luminescence and photo-luminescence from strained SiGe/Si quantum well

Photo-luminescence and electro-luminescence from step-graded index SiGe/Si quantum well grown by molecular beam epitaxy is reported. The SiGe/Si step-graded index quantum well structure is beneficial to the enhancing of electro-luminescence. The optical and electrical properties of this structure are discussed.

Influence of a tilted cavity on quantum-dot optoelectronic active devices

Quantum-dot laser diodes (QD-LDs) with a Fabry-Perot cavity and quantum-dot semiconductor optical amplifiers (QD-SOAs) with 7° tilted cavity were fabricated. The influence of a tilted cavity on optoelectronic active devices was also investigated. For the QD-LD, high performance was observed at room temperature. The threshold current was below 30 mA and the slope efficiency was 0.36 W/A. In contrast, the threshold current of the QD-SOA approached 1000 mA, which indicated that low facet reflectivity was obtained due to the tilted cavity design.A much more inverted carrier population was found in the QD-SOA active region at high operating current, thus offering a large optical gain and preserving the advantages of quantum dots in optical amplification and processing applications. Due to the inhomogeneity and excited state transition of quantum dots, the full width at half maximum of the electroluminescence spectrum of the QD-SOA was 81.6 nm at the injection current of 120 mA, which was ideal for broad bandwidth application in a wavelength division multiplexing system. In addition, there was more than one lasing peak in the lasing spectra of both devices and the separation of these peak positions was 6-8 nm,which is approximately equal to the homogeneous broadening of quantum dots.

基于文献计量分析的LED知识图谱及产业化对策

LED照明是当前最具发展前景的高技术领域之一.本文运用文献计量相关分析方法对LED的历史文献进行分析,通过绘制多维尺度分析图谱和核心关键词关联知识图谱,挖掘当前LED的技术成熟度、研究热点和关键技术点等信息,得出LED技术目前主要集中宽带隙材料、发光类型及特性、有机发光和超亮度LED研发上;氮化镓(GaN)、电致发光(electroluminescence)、光致发光(photoluminescence)、白光(White LED)等在整个LED研究中处于中心和控制大多数信息流向的地位.最后,本文通过国别分析判断我国LED产业的实力水平,最终为我国的LED技术产业化发展提供建议.

Array for 980nm Vertical Cavity Surface Emitting Diodes and Detectors

Both the vertical cavity surface emitting diodes and detectors are fabricated by using the epitaxial wafer with resonant cavity structure. Their characteristics are analyzed. The light emitters have high spectral purity of 4.8nm and high electroluminescence intensity of 0.7mW while injection current is 50mA. A 1*16 array of surface emitting light device is tested on line by probes and then used for module. The light detectors have wavelength selectivity and space selectivity. The required difference in input mirror reflectivity between emitters and detectors can easily be achieved though varying the numbers of top DBR period by etching.

MOCVD growth of cubic GaN: Materials and devices

Many impressive progresses have been made recently on the growth of cubic-phase GaN by MBE and MOCVD. In this paper, some of our recent progress will be reviewed, including the growth of high quality cubic InGaN films, InGaN/GaN heterostructure blue and green LEDs. Cubic-phase GaN films were grown on GaAs (100) substrates by MOCVD. Growth conditions were optimized to obtain pure cubic phase GaN films up to a thickness of 4 mum. An anomalous compressive strain was found in the as-grown GaN films in spite of a smaller lattice constant for GaN compared with that of GaAs substrates. The photoluminescence FWHM of high quality InGaN epilayers was less than 100 meV The InGaN/GaN heterostructure blue LED has intense electroluminescence with a FWHM of 20 nm.