微纳结构增强GaN基LED发光效率的研究

发布时间：2018-01-11 05:15

本文关键词：微纳结构增强GaN基LED发光效率的研究　出处：《江南大学》2017年硕士论文　论文类型：学位论文

【摘要】：随着GaN基发光二极管(LEDs)的快速发展,LED以其优越的性能正逐渐替代传统照明器件被广泛应用在各个领域,它不仅具备发光效率高、响应时间短、光谱可调范围大、寿命长等优点,同时还具有材料无污染、节能等诸多优点。尽管LED的商业应用已经比较普遍,价格也比较低廉,但其仍面临需要克服外量子效率低的问题,关键在于如何解决由于GaN材料和外界空气界面处全反射角所引起的光提取率低问题。目前常用的方法有光子晶体、倒装芯片、透明衬底、表面粗化、等离激元等技术。本文主要是通过在半导体表面制备微纳结构增强GaN基LED的发光效率,主要分为沉积金属薄膜、金属颗粒和刻蚀三个部分,并对几种微纳结构下的LED光致发光谱进行对比分析。具体研究工作和相关结果如下:1.利用时域差分有限元的方法(FDTD)研究了金属纳米粒子增强GaN紫外LED的光提取率。结构包含不同尺寸、间距的Al纳米粒子,同时还包括非对称结构的Al纳米粒子。通过调节纳米粒子的尺寸和间距可以改变光谱的响应范围,发现电场增强分布和峰值的位置也和纳米粒子的结构对称性有关。通过调节非对称结构的纳米粒子参数可以获得较大增强比例,为获得高效的深紫外LED提供参考价值。2.利用磁控溅射镀膜仪设备在GaN基LED外延片表面沉积不同厚度的金属Ag薄膜,采用光致发光谱来表征外延片的发光效率,得出了三种不同厚度的金属薄膜对其发光效率的影响,FDTD仿真结果验证了在金属表面出现场增强的效果。3.通过对金属薄膜进行退火处理得到金属纳米粒子,实验研究了三种不同直径的金属Ag纳米粒子对GaN基LED发光效率的影响,同时使用FDTD软件从理论上计算了三种直径Ag纳米颗粒的消光光谱,计算结果和实验结果能够较好的吻合。同时电场增强在Ag纳米颗粒周围的效果更加明显,与预期一致。其PL光谱的增强比例最大提升219%。4.采用电感耦合等离子体技术(ICP)对GaN基LED的P型层进行刻蚀,经过ICP刻蚀后的LED器件发光效率明显增强,接着在刻蚀后的纳米线结构上沉积金属颗粒,并将实验结果与前面两种实验方式进行对比。对量子阱进行PL测试发现,对比原位外延片其PL光谱在峰值处增加了224%,是镀银纳米颗粒样片的1.2倍,表明在Ag纳米颗粒和纳米线直接有很强的表面等离激元耦合和散射作用。
[Abstract]:With the rapid development of LEDs, LEDs have been widely used in various fields because of their superior performance. They not only have high luminous efficiency. LED has many advantages, such as short response time, wide spectrum adjustable range, long life, no pollution of materials, energy saving and so on. Although the commercial application of LED is already relatively common, the price is also relatively low. However, it is still faced with the need to overcome the problem of low external quantum efficiency. The key lies in how to solve the problem of low optical extraction rate caused by the total reflection angle between GaN material and external air interface. At present, the commonly used methods are photonic crystal, flip chip, transparent substrate, and surface coarsening. In this paper, the luminescence efficiency of GaN based LED is enhanced by fabricating micro and nano structure on semiconductor surface, which is mainly divided into three parts: deposition metal film, metal particle and etching. The LED photoluminescence spectra of several micro and nano structures are compared and analyzed. The specific research work and related results are as follows: 1. Using the finite element method of time-domain difference (FDTD). The optical extraction rate and structure of metal nanoparticles enhanced GaN UV LED were studied. The response range of the spectrum can be changed by adjusting the size and spacing of the nano-particles. It is found that the distribution of electric field enhancement and the position of peak value are also related to the structure symmetry of the nanoparticles, and a large proportion of the nanoparticles can be obtained by adjusting the parameters of the asymmetric structure. In order to obtain highly efficient deep ultraviolet (LED), reference value is provided. 2. Using magnetron sputtering equipment, Ag thin films of different thickness are deposited on the surface of GaN based LED epitaxial wafers. Photoluminescence spectra were used to characterize the luminescence efficiency of the epitaxial wafers, and the effects of three kinds of metal films with different thickness on the luminescence efficiency were obtained. FDTD simulation results verify the effect of in-situ enhancement on the metal surface. 3. The metal nanoparticles are obtained by annealing the metal film. The effects of three kinds of metal Ag nanoparticles with different diameters on the luminescence efficiency of GaN based LED were studied experimentally. The extinction spectra of three Ag nanoparticles with different diameters were calculated theoretically by using FDTD software. The calculated results are in good agreement with the experimental results, and the effect of electric field enhancement around Ag nanoparticles is more obvious. The enhancement ratio of PL spectrum is maximum 219.4.The P-type layer of GaN based LED is etched by inductively coupled plasma technique. The luminescence efficiency of LED device after ICP etching is obviously enhanced, and then the metal particles are deposited on the nanowire structure after etching. The PL spectra of the quantum wells are increased by 224% at the peak compared with the in situ epitaxial wafers. The results show that Ag nanoparticles and nanowires have strong surface coupling and scattering.
【学位授予单位】：江南大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TN312.8

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