The Investigation Of GaN Nanostructures Through Ammoniating The Ga₂O₃/Al Films Deposited On Si Substrates By R.f Magnetron Sputtering

Due to the novel characteristics of nanosemiconductor exhibits, more researches focus on the various semiconductor nanostructures. Nanowires, nanobelts, nanoribbons, nanorods, are a new class of quasi-one-dimensional materials that have been attracting a great deal of research interest in the last few years. Nanocircuits built of semiconductor nanowires were declared a"breakthrough in science"by Science magazine in 2001.Nature magazine recently published a report claiming that"Nanowires, nanorods, nanowhiskers, it does not matter what you call them, they are the hottest property in nanotechnology". There is no doubt that nanowirebased quasi-one-dimensional materials will become the new focal point of research in the next decades. Gallium nitride (GaN) has been a significant wide-band gap semiconductor due to its applications in blue light emission and high power electronic devices. Along with recent explosive research interest in nanotechnology, there have been extensive efforts to synthesize GaN one-dimensional nanosturctures, such as nanowires and nanobelts (or nanoribbons), for nanodevice applications.Gallium nitride is a kind of semiconductor with wide (3.39eV) and direct band-gap, which makes it entrenched itself in the application of short-wave photoelectric devices. GaN and its related alloys, which have the continuous and adjustable band-gaps from 1.6eV (InN) to 6.2eV(AlN), are eligible materials to produce short wave laser devices (LDs). So far GaN-based diodes of near ultraviolet, blue and green light have been manufactured for commercial purpose. And the investigation to GaN-based LDs and detectors are now in the ascendant. For its wider band gap, GaN LDs have shorter wavelength, which can enhance the storage density of LD memory greatly. Moreover, worth the whistle, GaN-based white light LEDs, with lower energy consumption, higher efficiency, longer lifetime and lower price, are truly luminescence resources, which are expected to substitute traditional incandescent lamp and take the primary role in future lighting. That will changed our life greatly!Owning to the good characteristics and immense potential applications, GaN is called the typical of the third semiconductor. One-dimensional (1D) GaN nanostructures, with many novel properties, have an applied potential in 1D systems. The investigations of 1D nanostructure of GaN made up the most active researching area in the world. Our research was focused on the 1 D GaN nanostuctures on the Si material.Si is regarded as one of the most promising substrate for growing the GaN material due to its large size, high quality and relatively low cost. Furthermore, the GaN epitaxy on Si will facilitate the integration of microelectronics and optoelectronics. However, there are several difficulties to grow single crystalline GaN films directly on the Si substrate: 1) the high lattices mismatch (17%) and the differences in the thermal expansion coefficient (100%) between GaN (in wurtzite structure) and Si; 2) the poor wetting of GaN on Si; 3) he nitridation of the Si surface during growth of nitrides.So it is very difficult to grow high quality crystalline GaN directly on Si substrates. In this paper, we chose the active metal aluminum as the buffer and fabricated GaN low dimensional nanostructure material by magnetron sputtering and ammoniating. In contrast, we also fabricated GaN nanostructures on the oxidized alumina buffer instead of sapphire. The detailed growth procedure of the GaN nanostruture is presented. The effects of the process parameters on the properties of GaN nanostructures are discussed. The optimum thickness of the buffer layer and the optimum annealing temperature and time for the fabrication of GaN nanostructure by the method are investigated.According to the different morphologies of GaN low dimensioanal nanostructures at different growth times, we probe the growth mechanism of GaN low dimensioanal nanostructures materials. The context of the thesis can be described as follows:1. The GaN low dimensional nanostructure material was fabricated by ammoniating the Ga₂O₃/Al films deposited by r.f magnetron sputtering. The aluminum film were deposited onto the Si(111) substrate before the deposition of Ga₂O₃.We find that the buffer of aluminum enhance the density,crystalline quality and the surface smoothness of GaN low dimensional nanostructures on the Si(111) substrates under the same conditions of thickness of Ga2O3 films, temperature and time of ammoniating.2. The best thickness of Al buffer under the same ammoniating time and temperature, on which we got the better crystalline quality nanostructure material was about 20nm.And the best thickness of the oxidized Al buffer is 300nm.It is worse for the fabrication of the nanostructures and the formation of the smooth surface on the bigger or smaller thickness buffer.3. Under the best conditions of ammoniating temperature and time, we got the GaN nanowires with approximate diameter of 50nm through ammoniating the Ga₂O₃ films on the aluminum buffer with the same thickness. According to the measurement of XRD, we testified the nanowires we got in our experiment hexagonal GaN and the selected area electron diffraction (SAED) analysis shows the single crystalline structure of them. They were found have a growth orientation of [100] and their axes have a 50°angle with [100] with the assistance of high resolution electron microscopy(HRTEM).4. The morphology varies with different ammoniating times: the presentation of the big particles---gathering of rods ----gathering of wires--column of plain pillars. We probe the changes of growth mechanism simply and measured and indexed the GaN nanostructures.5. We try to explore the grow mechanism of AlN films by ammoniating the Al films on Si(111) substrates deposited by r.f. magnetron sputtering.