【作者】 杨冬；

【导师】 许并社；

【作者基本信息】 太原理工大学 ， 材料学， 2007， 硕士

【摘要】 氮化镓是一种良好的宽带隙Ⅲ-Ⅴ族化合物半导体材料，是当前世界上最先进的半导体材料之一。在室温下，氮化镓的禁带宽度为3.4 eV，是制作光电子器件，蓝、绿发光二极管(LEDs)和激光二极管(LDs)的理想材料。这类光源在高密度光信息存储、高速激光打印、全色动态高亮度光显示、固体照明、信号探测、通讯等方面有着广阔的应用前景和巨大的市场潜力。此外，氮化镓也是制作高温、高频、大功率器件的理想材料。目前，氮化镓材料己经成为世界各国研究的热点。金属有机化学气相沉积(MOCVD)、分子束外延(MBE)和氢化物气相外延(HVPE)等方法已经成为制备氮化镓材料的主流工艺，其中以MOCVD工艺使用的最为广泛。采用上述方法制备氮化镓材料，设备昂贵，工艺复杂，很大程度上限制了氮化镓材料的制备、生产和应用。现在，国际上许多科研机构正在探索新的工艺方法，试图在合适的衬底上制备高质量的氮化镓薄膜。近几年来，由于一维氮化镓纳米结构在可见光和紫外光光电子器件方面的应用前景十分诱人，氮化镓一维结构的合成己经备受关注，国际上掀起了一维氮化镓纳米结构材料的研究热潮。本文采用简单的化学气相沉积方法，在硅衬底上合成了高纯的一维氮化镓纳米结构和氮化镓晶体薄膜，分析了合成产物的组分和结构，探讨了化学气相沉积法合成一维氮化镓纳米结构的生长机制与影响因素。1、以金属镓和氨气为原料，物理蒸发镀金属镍为催化剂，硅为衬底，用化学气相沉积方法在950℃合成氮化镓纳米带，结果表明纳米带为纤锌六方结构晶体，宽度在50nm到200nm范围内，宽厚比大约为1／20，长度达到几十微米，不均一的径向生长导致了带状结构的形成，其生长机理为VLS机理。2、以金属镓和氨气为原料，物理蒸发镀金属镍为催化剂，硅为衬底，用化学气相沉积方法在1050℃合成六角锥形氮化镓纳米结构，锥形结构为六方结构晶体，平均直径为500nm左右，长度为几个微米，其生长是由VLS和VS机理混合控制。3、以金属镓和氨气为原料，电镀金属镍为催化剂，硅为衬底，用化学气相沉积方法合成氮化镓纳米线，氮化镓纳米线呈现弯曲形状，表面光滑，长度达到几十微米，直径大概在20nm到200 nm范围内，其生长由VLS机理控制。4、以金属镓和氨气为原料，硅为衬底，不使用任何催化剂，用化学气相沉积方法合成蜿蜒曲折形状的氮化镓纳米线，该纳米线不如使用催化剂合成的氮化镓纳米线光滑，其长度达到几十微米，直径大概在30nm到150nm范围内，生长机理是VS机理。5、实验中发现衬底的表面形貌对产物的形貌有很大影响。在光滑的衬底表面容易形成纳米线，在粗糙的衬底表面容易形成纳米带。但是衬底的光滑程度和产物的形貌之间的关系还不是很清楚，需要有进一步的研究数据支持；升温速率对样品的形貌有很大影响，升温速率高的时候容易形成线(带)状的结构，而升温速率较低时容易形成薄膜形貌。6、氮化镓薄膜和其它一维形貌氮化镓结构，如纳米带环、纳米棒和纳米片等也被合成。更多还原

【Abstract】 GaN is an excellent wide band gap III—V compound semiconductor material and also one of the best advanced semiconductor materials. Having large direct energy band gap of 3.4 eV at room temperature, GaN is an ideal material for fabricating optoelectronic devices, especially blue and green light emitting diodes (LEDs) and laser diodes (LDs). This kind of materials have good potential application and great market demand in high density optical information memory, high speed laser print, high brightness dynamic, full color display, solid illumination, signal detector and communication. In addition, GaN attracts much attention for fabrication of high temperature, high frequency and high power devices. Presently, much attention is being paid to GaN materials all over the world. MOCVD, MBE, and HVPE have become dominating methods for growing GaN. Among these techniques, MOCVD has been widely used by researchers. However, GaN materials are not well prepared and applied in large scale because of the complicated growth technics and expensive equipments by above methods. Now, a lot of scientific research institutions are exploring new technique to grow high quality GaN film on appropriate wafer. For recently years, one-dimensional GaN nanostructure has gained considerable attention for its potential application both in visible light and ultraviolet light optoelectronic devices, one-dimensional GaN materials have become a worldwide focus.In this paper, high purity one-dimensional GaN structure and GaN film were synthesized on Si wafer by CVD, its composition and structure were analyzed, the growth mechanism and influencing factors of one-dimensional GaN growth were discussed.1. GaN nanobelts were synthesized by direct reaction of metallic gallium with flowing ammonia using physical evaporating Ni as catalyst on Si substrate via CVD at 950℃. Results indicated that as-synthesized nanobelts were single crystalline, hexagonal wurtzite structure GaN. Its widths were in the range of 50-200 nm, with the ratio of thickness to width to be about 1/20 and their lengths up to several tens of microns. The nommiformity radial growth was assumed to lead to beltlike nanostructure. The catalytic growth mechanism of GaN nanobelts was probably dominated by conventional VLS mechanism.2. Hexagonal cone-shaped GaN nanostructure were synthesized by direct reaction of metallic gallium with flowing ammonia using physical evaporating Ni as catalyst on Si substrate via CVD at 1050℃. Results indicated that as-synthesized structure were single crystalline, hexagonal wurtzite structure GaN. Its mean diameter is about 500 nm, with the lengths several microns. Its growth mechanism was probably dominated by conventional VLS and VS mechanism.3. GaN nanowires were synthesized by direct reaction of metallic gallium with flowing ammonia using electric plating Ni as catalyst on Si substrate via CVD. Results indicated that as-synthesized nanowires were curved, and had smooth surface. Its diameters were in the range of 20-100 nm, with the lengths several tens of microns. Its growth mechanism was probably dominated by conventional VLS mechanism.4. Zigzag GaN nanowires were synthesized by direct reaction of metallic gallium with flowing ammonia on Si substrate by CVD. Results indicated that as-synthesized nanowires were not smoother than nanowires as-synthesized using Ni as catalyst. Its diameters were in the range of 30-150 nm, with the lengths several tens of microns. Its growth mechanism was probably dominated by conventional VS mechanism.5. It was found that substrate surface is an important factor affecting product morphology. It is easy to form nanowires on smooth surface and form nanobelts on rough surface. However, the relationship between the smooth degree of substrate and product morphology has not been clear, which needs further investigation. And heating rate is also an important factor affecting product morphology, it was found that it is easy to form nanowire or nanobelt structure with high heating rate and form film morphology with low heating rate.6. GaN film and other morphologies such as nanobelt ring, nanorod, and nanosheet were also synthesized.更多还原