【作者】 李红；

【导师】 薛成山；

【作者基本信息】 山东师范大学 ， 微电子学与固体电子学， 2008， 硕士

【摘要】 GaN是一种十分优异的宽带隙Ш一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。室温下,GaN的禁带宽度为3.4eV,是制作光电子器件,尤其是蓝、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、固体照明光源、高亮度信号探测、通讯等方面有着广阔的应用前景和巨大的市场潜力。此外,GaN也是制作高温、高频、大功率器件的理想材料。进入90年代之后,随着材料生长和器件工艺水平的不断发展和完善,一些突破性技术的实现使GaN材料的研究空前活跃,GaN己经成为世界各国争相研究的热点。目前,金属有机气相沉积（MOCVD）、分子束外延（MBE）和氢化物气相外延（HVPE）等方法己经成为制备GaN的主流工艺,其中MOCVD使用的最为广泛。采用上述方法制备GaN,工艺复杂,设备昂贵,限制了GaN材料的制备、生产和应用。现在,国际上有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GaN薄膜。目前GaN基器件大多数制作在蓝宝石衬底上。由于蓝宝石价格昂贵、衬底自身绝缘且硬度大、器件工艺复杂、制作成本费用高,且由于它导热性能差,不利于大功率器件的制作,硅衬底则可以弥补这些不足。因此,开展Si基GaN薄膜材料的外延生长意义重大。虽然以Si为衬底的六方GaN材料的生长有一定难度,但由于其晶体质量高、价格低廉、易解理、导电性好和成熟的Si基集成技术等优点,成为蓝宝石衬底强有力的竞争者。本文介绍了采用氨化磁控溅射Ga₂O₃/Ta薄膜的方法在硅衬底上合成了GaN纳米结构的方法。并以扫描电镜（SEM）为主,结合透射电镜及高分辨电镜、X射线衍射、红外吸收等手段,研究了纳米线的形貌、显微结构、成分等,并对其生长机制进行了初步探索。研究了不同的氨化温度、不同的氨化时间和不同中间层厚度对GaN纳米线的影响。首先我们利用磁控溅射系统先在Si衬底上制备Ga₂O₃/Ta薄膜,然后在氨气氛围中退火制备GaN纳米结构。测试结果表明:合成的纳米结构为六方纤锌矿结构的GaN;氨化温度、氨化时间和Ta薄膜的厚度都对一维GaN纳米结构的结晶质量和形貌产生很大的影响。随着氨化温度的升高,GaN纳米结构的直径先减小并有棉絮状晶体生成,后来直径又增大且表面趋于相对光滑;纳米结构的结晶质量也逐渐提高。其中,退火温度为1000℃时,样品的结晶质量和表面形貌最佳。但是,当温度继续升高（高于1000℃）,氮化镓纳米线的数量会减少并且结晶质量也会下降。从氨化时间上看,10min所得结果相对较好。另外选用不同的中间层厚度,发现得到的纳米结构形貌各异,说明中间层的厚度对一维GaN纳米结构的合成也有很大的影响。GaN纳米结构的生长机制可初步归结为气体—液体—固体（VLS）生长机制,其中高温下Ta薄膜在高温下会破裂并会在Si衬底上形成纳米液滴,对GaN纳米线的生长起到重要作用。更多还原

【Abstract】 Gallium nitride (GaN) is an excellent chemical semiconductor material and also is one of the most advanced semiconductors in the world. In fact, GaN has been regarded as one of the most promising materials for the fabrication of opto-electronic devices operating in the blue and near-ultraviolet (UV) regions, for instance light-emitting diodes (LEDs) and laser diodes (LDs), because it has large direct energy band gap of 3.4 eV at room temperature. These light sources have promising applications and potential market demands for the high-density storage of opto-information, high-speed laser print, high-brightness and dynamic display in all colors, solid light sources, signal detectors and communication. In addition, GaN has been attracted much attention as a candidate for fabrication of high temperature, high frequency and high power devices. After 1990, the realization of some pivotally technieal methods and the development of materials growth and devices technics made GaN to be the research focus of the world. MOCVD, MBE and HVPE have become dominating techniques to grow GaN materials. Among these methods, MOCVD is the most important and widely used by researchers. But now large-scale application of GaN devices is confined for the reason of costly equipments and complicated technics. Many research institutes and universities in the world are trying to grow GaN materials with simple and lower cost methods.In this paper, GaN one-dimensional nanostructures were prepared through magnetron sputtering and ammoniating progress on Si (111) substrates. The morphology, microstructure, and components of nanostructures were analyzed through scanning electron microscopy (SEM), transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD), Fourier transformed infrared spectra (FTIR) and X-ray photoelectron spectra (XPS) and so on. We also have a primary discussion about the growth progress of GaN nanostructures.The effects on GaN nanostructures, which stem from various experimental conditions such as the thickness of the middle layer, ammoniating temperature and ammoniating time, were discussed.Firstly, Ga2O3/Ta film is deposited on Si (111) substrates by magnetron sputtering system, and then GaN nanostructures were fabricated through ammoniating. The results of these tests indicated that the as-synthesized GaN nanostructures were hexagonal GaN with wurtzite structure. The crystalline quality and morphology of GaN nanostructures were greatly influnced by the ammoniating temperature, ammoniating time and the thickness of the Ta films. With the increase of temperature, the diameter of GaN nanostructures was decreased and some batt-shaped crystals were formed, and then the diameter of GaN nanostructures was increased and these GaN nanostructures changed to be relative smooth. The crystalline quality of these GaN nanostructures was also improved. The samples annealed at 1000℃for 10min exhibited the best crystal quality and morphology. But the crystalline quality falled and the amount of these GaN nanostructures decreased when the temperature keep on increasing(above 1000℃).We can get the best results when the ammoniating time is 10min. Nanostructures with different morphology were fabricated by this sputtering-post-annealing technique with the help of Ta films with different thickness as middle layers. A VLS mechanism was possible valid in the growth process of GaN nanostructures in this method. The Ta film broke up, and then the liquid Ta nanodroplets which act as energetically favorable sites for absorption of gas-phase reactants are formed on the Si surface at high temperature, which may plays an important role in the formation of GaN nanostructures.更多还原