局域表面等离激元增强AlGaN基MSM型日盲紫外探测器

	局域表面等离激元增强AlGaN基MSM型日盲紫外探测器
	包广宏
学位类型	硕士
导师	黎大兵
	2014-11
学位授予单位	中国科学院大学
学位专业	凝聚态物理
关键词	Algan日盲紫外探测器表面等离激元 Al颗粒制备
摘要	随着科技的进步，紫外探测技术被广泛地应用在很多的方面。AlGaN 基日盲紫外探测器具有体积小、工作电压低、绿色环保和物理化学性质稳定等优点，因而在预警监测、生化医药、天文等领域有着巨大的应用前景。然而,与传统的紫外光电倍增管相比，AlGaN基日盲紫外探测器的响应度依然很低，这已成为制约其发展和应用的关键。目前，AlGaN半导体材料的位错密度高达109cm-2，通过改善AlGaN材料的质量来提高响应度的方法仍然具有很大的困难，而利用金属纳米颗粒产生的局域表面等离激元来提高探测器的光吸收效率已成为一个研究热点。本文研究了表面等离激元对AlGaN基日盲紫外探测器响应度的增强作用，对促进AlGaN基紫外探测器的发展和应用有着重要的意义。本文用MOCVD 在蓝宝石衬底上生长了高质量的AlGaN材料，尝试了SiO2掩膜沉积Al阵列以及电子束蒸发制备Al纳米颗粒的方法，最终成功获得了大小可控的Al纳米颗粒。器件上采用标准光刻工艺制备MSM结构探测器。电极为50nm的Ni金属层，在氮气氛围下450℃退火180s。光谱响应测试显示当Al颗粒的大小约为60nm时，探测器峰值响应度（288nm）增加了超过2倍，随着Al颗粒直径的减小，峰值响应度增加的倍数也逐渐减少。暗电流的测试表明不同大小的Al颗粒都能略微降低探测器的暗电流，这主要是由于Al2O3外壳对螺位错的钝化作用，减少了漏电通道。本文取得的研究成果如下： 1. 利用时域有限差分法模拟了不同大小Al纳米颗粒的消光光谱，分析了Al颗粒与入射光的耦合规律，进一步研究了Al2O3使消光光谱红移的现象，在此基础上了解了表面等离激元对探测器性能的增强作用。 2. 探索了多种制备Al纳米颗粒的方法，并成功掌握了利用电子束蒸发制备大小可控Al纳米颗粒的条件。 3. 制备了AlGaN基MSM结构日盲紫外探测器，研究了不同大小的Al颗粒对探测器响应度的增强规律及对暗电流的影响。实验发现60nm的Al颗粒对探测器的增强效果最明显，这是由于金属颗粒的散射作用以及由Al颗粒引起的局域表面等离激元耦合共振增加了半导体材料的光吸收，使光生电子空穴对的数量增加，从而增强了光响应度。而暗电流受Al颗粒的影响很小，主要是Al2O3能钝化位错，减少漏电通道。
其他摘要	With the remarkably development of science and technology, ultraviolet detection technology has been widely used in many fields. AlGaN based solar-blind ultraviolet (SB-UV) detectors have wide applications in early warning monitoring, medicine, astronomy due to the advantages of being solid-state and of small size, low working voltage, with good physical and chemical stability, thereby saving energy and having a long lifetime. However, the responsivity of AlGaN based SB-UV detectors are still low compared with the traditional UV photomultiplier which have restrained their development and application. At present, the dislocation density of AlGaN material is as high as 109 cm–2. This problem can hardly be resolved before more suitable substrates are used. It still has a lot of difficulties in improving the responsivity by improving the quality of the AlGaN materials. Recently, the interaction of light with metallic nanoparticles gives rise to a diversity of profound effects on improving the performance of optoelectronic devices. The plasmonic phenomena offer new opportunities to engineer the performance of photodetectors via improved coupling between optical processes in the device active region and incident or emitted light. In this paper, the enhancement mechanism of localized surface plasmons (LSPs) is also explored and discussed which has important significance to the promote development and application of AlGaN SB-UV detectors. In this paper, the undoped AlGaN epilayer was grown on (0001) sapphire substrate by metal-organic chemical vapor deposition (MOCVD). SiO2 mask and electron beam evaporation method were tried to depositing Al nanoparticle arrays. Finally Al nanoparticles with controllable size are successfully made. The detector with MSM structure is prepared by standard photolithography process. Nickel (Ni) (50 nm) Schottky contacts were fabricated for AlGaN MSM interdigitated contacts and then the samples were treated by rapid thermal annealing at 450°C for 180s under nitrogen atmosphere. Spectral response tests show that when the diameter of the particle is about 60 nm, the strongest responsivity (288 nm) increased more than 2 times. With the decrease of the Al particle, the peak response increased multiples also gradually reduced. Dark current tests show that Al particles of different sizes can slightly reduce the dark current of the detector. This is mainly due to the Al2O3 shell which passivated the screw dislocation, reducing the leakage passage. The results of the article research are as follows: 1 The extinction spectrum of Al nanoparticles with different sizes were simulated by finite difference time domain method. The coupling law between Al particles and the incident light was analyzed. A further study which the effect of Al2O3 on the redshift of extinction spectrum was carried on. At last we study the enhancement effect of surface plasmon resonance on detectors’ performance. 2 We explored the various kinds of methods for preparation of Al nanoparticles. At last we successfully mastered the preparation for Al nanoparticles with controllable size by electron beam evaporation. 3 The AlGaN based SB-UV detector with MSM structure was prepared. The influence of Al particles with different sizes on the response and dark current of the detector are studied. It was found that the peak responsivity is the highest for the sample with the diameter of Al NPs being 60 nm and the responsivity increased from 0.141 A/W to 0.288 A/W, more than 2 times enhancement. This is due to the scattering effect of the Al particles and local surface plasmon resonance caused by Al particles. Then the localized electric field enhancement effect and related scattering effect results in more electron-hole pairs generated and thus a higher responsivity. The dark current of the detectors with Al NPs is a little bit reduced compared with that without Al NPs. This is due to the passivation effect of the Al2O3 shell which can decrease the leakage because of their terminating the screw dislocations.
语种	中文
文献类型	学位论文
条目标识符	http://ir.ciomp.ac.cn/handle/181722/44636
专题	中科院长春光机所知识产出
推荐引用方式 GB/T 7714	包广宏. 局域表面等离激元增强AlGaN基MSM型日盲紫外探测器[D]. 中国科学院大学,2014.

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