GaN纳米材料的制备与表征
发布时间：2018-11-22 06:01
【摘要】：GaN材料与SiC、金刚石等半导体材料一起被称为第三代半导体材料,GaN具有宽的禁带宽度、高的击穿电压、高电子饱和速率及抗辐射能力,是发展高功率、高频、高温电子器件的理想材料,而且GaN发光效率较高,在制作蓝绿光发光器件及半导体激光器等方面有着重要应用。与体材料相比纳米结构具有以下优点,首先纳米结构中存在应力弛豫会降低量子限制斯塔克效应,其次纳米柱侧壁为光子的释放提供了更多的路径,具有更高的出光效率。GaN纳米结构在固态照明领域的应用亦成为近年来研究的热点。关于GaN纳米柱的制备有很多方法,包括VLS生长法、光刻法以及纳米压印法等,本文采用自组织Ni纳米岛作为掩膜利用ICP刻蚀系统制备GaN纳米柱,这种方法不同于以前在ICP刻蚀前需要用光刻技术来制备均匀周期性的纳米模板,需要消耗高昂的费用。用自组织的Ni纳米颗粒作掩膜进行纳米结构的制备,通常是在样品上生长一层Ni膜,然后在RTA中进行快速热退火,使其形成Ni纳米岛,以此作为后续制备纳米结构的掩膜。此外在实验过程中还可以通过控制最初生长的Ni膜的厚度、快速退火的时间及温度等参数来控制最终形成的Ni纳米岛的尺寸、密度以及占空比等分布情况,而且这种方法成本较低在大规模制备纳米柱过程中可广泛使用。本文即是采用这种方法在ICP系统中进行GaN纳米柱制备研究了不同刻蚀条件对纳米柱刻蚀速率及发光性质的影响,并用KOH对样品进行处理,所得结果如下：1.用自组织Ni纳米岛作为掩膜利用ICP刻蚀系统制备GaN纳米柱,并研究了刻蚀过程不同刻蚀参数变化对纳米柱刻蚀速率以及发光性质的影响,随着RF、ICP功率的升高,刻蚀速率也在不断的增高,这分别与刻蚀过程中物理轰击增强和反应离子浓度的增加有关,但发光强度并不随RF、ICP的变化呈线性关系变化2.刻蚀之后纳米柱的发光强度与薄膜相比明显增强,除此之外还发现刻蚀之后得到的GaN纳米柱呈锥形结构,这是因为在纳米柱的刻蚀过程中存在横向刻蚀,并非理想的垂直刻蚀,而且刻蚀后纳米柱的尺寸比刻蚀模板要小一些,这是因为在刻蚀过程中作为刻蚀掩膜的Ni纳米颗粒也会被刻蚀。为了研究刻蚀前后应力变化情况,分别测量了GaN薄膜和GaN纳米柱的拉曼光谱,结果发现相对于GaN薄膜材料而言,GaN纳米柱存在应力释放3.用KOH对样品进行处理,经KOH处理的纳米柱其发光强度较处理之前进一步增强,通过变温PL谱的测量可知发光强度增强是由于内量子效率的增强引起的,KOH腐蚀后内量子效率的增加是因为在纳米柱刻蚀过程中会在样品表面产生刻蚀损伤,这些刻蚀损伤作为非辐射复合中心会影响发光,而KOH腐蚀过程中会腐蚀掉这些损伤
[Abstract]:GaN materials, along with SiC, diamond and other semiconductor materials, are called the third generation semiconductor materials. GaN has wide band gap, high breakdown voltage, high electron saturation rate and radiation resistance, which is the development of high power and high frequency. GaN is an ideal material for high temperature electronic devices and has high luminescence efficiency. It has important applications in making blue-green photoluminescence devices and semiconductor lasers. Compared with bulk materials, nanostructures have the following advantages: firstly, the stress relaxation in nanostructures can reduce the quantum confinement Stark effect, and secondly, the lateral walls of the nanocolumns provide more paths for the release of photons. The application of GaN nanostructures in solid-state lighting has become a hot topic in recent years. There are many methods for the preparation of GaN nanorods, including VLS growth, lithography and nano-imprint. In this paper, self-organized Ni nanolayers are used as masks to fabricate GaN nanorods by ICP etching system. This method is different from that before ICP etching, which requires photolithography to fabricate uniform periodic nanotemplates, which requires high cost. The self-organized Ni nanoparticles are used as the mask for the preparation of nanostructures. Usually, a layer of Ni films is grown on the samples, and then annealed in RTA to form Ni nanoislands, which can be used as a mask for the subsequent preparation of nanostructures. In addition, the size, density and duty cycle distribution of the resulting Ni nanoliths can be controlled by controlling the thickness of the initial Ni films, the time and temperature of the rapid annealing, and so on. Moreover, this method can be widely used in the preparation of nano-columns at low cost. In this paper, the effects of different etching conditions on the etching rate and luminescence properties of GaN nanorods were studied by using this method in ICP system. The samples were treated with KOH. The results are as follows: 1. Self-organized Ni nanowires were used as masks to prepare GaN nanorods by ICP etching system. The effects of different etching parameters during etching on the etching rate and luminescence properties of nano-columns were studied. With the increase of RF,ICP power, the etching rate and luminescence properties of the nano-columns were studied. The etching rate is also increasing, which is related to the enhancement of physical bombardment and the increase of reaction ion concentration, but the luminescence intensity does not change linearly with the change of RF,ICP. After etching, the luminescence intensity of the nanocrystalline column is obviously higher than that of the thin film. In addition, it is also found that the GaN nanocolumn obtained by etching is conical, which is due to the existence of transverse etching in the etching process of the nanocrystalline column, which is not an ideal vertical etching. Moreover, the size of the nano-column is smaller than that of the etching template, because the Ni nanoparticles, which are used as the etching mask, are also etched during the etching process. In order to study the stress changes before and after etching, the Raman spectra of GaN film and GaN nanocolumn were measured, and the results showed that there was stress release in GaN nanocrystalline column compared with GaN film material. The luminescence intensity of the nano-column treated with KOH was further enhanced by KOH treatment. The measurement of PL spectrum at variable temperature showed that the enhancement of luminescence intensity was caused by the enhancement of internal quantum efficiency. The increase in quantum efficiency after KOH etching is due to the etching damage on the surface of the sample during the etching process of the nanoscale column, which acts as a non-radiative recombination center to affect the luminescence, while the KOH etching process corrodes the damage.
【学位授予单位】：南京大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TB383.1
本文编号：2348300
[Abstract]:GaN materials, along with SiC, diamond and other semiconductor materials, are called the third generation semiconductor materials. GaN has wide band gap, high breakdown voltage, high electron saturation rate and radiation resistance, which is the development of high power and high frequency. GaN is an ideal material for high temperature electronic devices and has high luminescence efficiency. It has important applications in making blue-green photoluminescence devices and semiconductor lasers. Compared with bulk materials, nanostructures have the following advantages: firstly, the stress relaxation in nanostructures can reduce the quantum confinement Stark effect, and secondly, the lateral walls of the nanocolumns provide more paths for the release of photons. The application of GaN nanostructures in solid-state lighting has become a hot topic in recent years. There are many methods for the preparation of GaN nanorods, including VLS growth, lithography and nano-imprint. In this paper, self-organized Ni nanolayers are used as masks to fabricate GaN nanorods by ICP etching system. This method is different from that before ICP etching, which requires photolithography to fabricate uniform periodic nanotemplates, which requires high cost. The self-organized Ni nanoparticles are used as the mask for the preparation of nanostructures. Usually, a layer of Ni films is grown on the samples, and then annealed in RTA to form Ni nanoislands, which can be used as a mask for the subsequent preparation of nanostructures. In addition, the size, density and duty cycle distribution of the resulting Ni nanoliths can be controlled by controlling the thickness of the initial Ni films, the time and temperature of the rapid annealing, and so on. Moreover, this method can be widely used in the preparation of nano-columns at low cost. In this paper, the effects of different etching conditions on the etching rate and luminescence properties of GaN nanorods were studied by using this method in ICP system. The samples were treated with KOH. The results are as follows: 1. Self-organized Ni nanowires were used as masks to prepare GaN nanorods by ICP etching system. The effects of different etching parameters during etching on the etching rate and luminescence properties of nano-columns were studied. With the increase of RF,ICP power, the etching rate and luminescence properties of the nano-columns were studied. The etching rate is also increasing, which is related to the enhancement of physical bombardment and the increase of reaction ion concentration, but the luminescence intensity does not change linearly with the change of RF,ICP. After etching, the luminescence intensity of the nanocrystalline column is obviously higher than that of the thin film. In addition, it is also found that the GaN nanocolumn obtained by etching is conical, which is due to the existence of transverse etching in the etching process of the nanocrystalline column, which is not an ideal vertical etching. Moreover, the size of the nano-column is smaller than that of the etching template, because the Ni nanoparticles, which are used as the etching mask, are also etched during the etching process. In order to study the stress changes before and after etching, the Raman spectra of GaN film and GaN nanocolumn were measured, and the results showed that there was stress release in GaN nanocrystalline column compared with GaN film material. The luminescence intensity of the nano-column treated with KOH was further enhanced by KOH treatment. The measurement of PL spectrum at variable temperature showed that the enhancement of luminescence intensity was caused by the enhancement of internal quantum efficiency. The increase in quantum efficiency after KOH etching is due to the etching damage on the surface of the sample during the etching process of the nanoscale column, which acts as a non-radiative recombination center to affect the luminescence, while the KOH etching process corrodes the damage.
【学位授予单位】：南京大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TB383.1
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