Growth and characterization of 0.8-mu m gate length AlGaN/GaN HEMTs on sapphire substrates

AlGaN/GaN high electron mobility transistor (HEMT) structures were grown on 2 inch sapphire substrates by MOCVD, and 0.8-mu m gate length devices were fabricated and measured. It is shown by resistance mapping that the HEMT structures have an average sheet resistance of approximately 380 Omega/sq with a uniformity of more than 96%. The 1-mm gate width devices using the materials yielded a pulsed drain current of 784 mA/mm at V-gs=0.5 V and V-ds=7 V with an extrinsic transconductance of 200 mS/mm. A 20-GHz unity current gain cutoff frequency (f(T)) and a 28-GHz maximum oscillation frequency (f(max)) were obtained. The device with a 0.6-mm gate width yielded a total output power of 2.0 W/mm (power density of 3.33 W/mm) with 41% power added efficiency (PAE) at 4 GHz.

Intraband absorption in the 8-12 mu m band from Si-doped vertically aligned InGaAs/GaAs quantum-dot superlattice

Normal-incident infrared absorption in the 8-12-mu m-atmospheric spectral window in the InGaAs/GaAs quantum-dot superlattice is observed. Using cross-sectional transmission electron microscopy, we find that the InGaAs quantum dots are perfectly vertically aligned in the growth direction (100). Under the normal incident radiation, a distinct absorption peaked at 9.9 mu m is observed. This work indicates the potential of this quantum-dot superlattice structure for use as normal-incident infrared imaging focal arrays application without fabricating grating structures. (C) 1998 American Institute of Physics. [S0003-6951(98)01151-6].

An 8-b 1-GSmaples/s CMOS cascaded folding and interpolating ADC

This paper presents an 8-bit low power cascaded folding and interpolating analog-to-digital converter (ADC). A reduction in the number of comparators, equal to the number of times the signal is folded, is obtained. The interleaved architecture is used to improve the sampling rate of the ADC. The circuit including a bandgap is implemented in a 0.18-mu m CMOS technology, and measures 1.47 mm X 1.47 mm (including pads). The simulation results illustrate a conversion rate of 1-GSamples/s and a power dissipation of less than 290mW.

波长8 μm 分布反馈量子级联激光器的研究

Submitted by 阎军 (yanj@red.semi.ac.cn) on 2010-06-07T07:15:25Z No. of bitstreams: 1 张伟--波长 8 μm分布反馈量子级联激光器的研究.pdf: 39254721 bytes, checksum: f62d5575b2849ea4ec14ec33e78dd9f6 (MD5)

非线性放大环形镜“8”字腔光纤激光器实验研究

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含8－羟基喹啉和噁二唑发光材料的合成与表征

本论文以提高有机／聚合物电致发光材料的发光效率为目的，通过改善发光材料分子的载流子传输平衡、增大分子体积为手段来减小荧光淬灭，设计并合成了一系列新型结构的络合物和聚合物。发现了一种合成五配位8-轻基喳琳铝络合物和双核铝8-轻基喳琳络合物的新方法，在分子中引入了电子和空穴传输基团改善了分子的载流子传输平衡，设计并合成了新型大体积的分子，提高了材料的发光效率，并系统地研究了分子结构与发光波长和发光效率的关系。主要工作如下：1发现了一种合成五配位8-经基喳琳铝络合物和双核铝8-经基喳琳络合物的新方法，克服了没有2一甲基的空间位阻作用很难形成五配位8-轻基喳琳铝络合物的困难。2合成了五配位2-甲基-8-轻基喳琳铝络合物并引入了具有不同空穴传输能力的第二配体。结果表明，与A 1 q;,相比，2-甲基-8-经基喳琳的引入导致了五配位络合物发光的蓝移，同时具有空穴传输能力的三苯胺基团的引入使电致发光器件的效率降低。3设计并合成了五配位8-轻基喳琳铝络合物，同时与Alq做了对比研究。研究发现，这一系列五配位络合物发射绿色荧光，五配位8-轻基喳琳铝络合物的发光波长主要由第一配体决定。4以五配位2-甲基-8-轻基喳琳铝和五配位8-轻基喳琳铝络合物为发光层制备了双层器件。结果表明，五配位8-经基喳琳铝络合物的电致发光波长主要由第一配体决定，第二配体只起到微弱的调节作用；第一配体对器件的发光效率起决定性的作用，第二配体的结构对络合物器件发光效率的影响在同一系列络合物中表现得非常明显。5从增加分子体积能够减小分子之间聚集，增强荧光效率这一观点出发，合成了具有双核铝的8一TTA-基喳琳络合物Me-DAlqz和PPv-DAlq3,用Me-DAlq,作发光层制备了双层器件，并与Alq_3i和AIMq_3作了对比研究。结果表明，DA 1 q,双层器件中的发光效率比Alq_3器件的性能稍高一些，证明了大体积分子能够增加荧光效率的观点。6合成了含有空穴传输性能的三苯胺基团的嗯二吟配体，并用其合 成了金属络合物。这些络合物发射蓝色的荧光，与不带三苯胺的德二哇金属络合物在溶液中发基本相同波长的荧光。但在薄膜和单层电致发光器件中，络合物的荧光发生了不同程度的红移。含三苯胺络合物的单层器件发光效率高于不含三苯胺络合物的单层器件的效率，证实了三苯胺的引入改进了载流子的传输平衡。7合成了系列嗯二哇基团两侧带有蔡环的金属络合物并以这些络合物为发光层制备了双层有机电致发光器件。结果表明，蔡环的引入导致了嗯二哇金属络合物在薄膜状态和电致发光器件中的发光波长比在溶液中的发光波长有了很大的红移。8设计并合成了既具有空穴传输性能又具有电子传输性能的蓝色发光聚合物。用电化学方法证明了它们具有两极性质，表明嗯二哇的引入增加了聚合物的电子传输能力。