New process for formation of gallium nitride thin films locally on selected areas

作为一种制备无氢氮化镓（GaN）薄膜的新方法，研究了氮气氛下的离子束直接沉积法。在氮自由基气氛下，用100 eV Ga离子束辐照Si（111）基片后，用X射线光电子能谱（XPS）研究了沉积材料的成分和化学键性质。在氮自由基下沉积的Ga的XPS光谱与外延生长的GaN参考的非常相似，表明使用本方法形成GaN薄层的可能性。由于采用纯N_2气体作为氮自由基源，因此沉积材料中不应掺入杂质碎片。结果表明，采用本方法可以在SiN薄膜的最外层形成无氢GaN层，此外，我们还报道了用低能（60-200 eV）Ga离子辐照在SiN薄膜的最外层形成GaN层。结果表明，Ga离子确实注入到了绝缘的SiN表面，Ga的XPS信号位置移动到了20.2eV，表明存在Ga-N键。由于所用的离子能量足够大以破坏Si-N键，这一结果表明N原子比Si原子更容易与注入的Ga原子键合。这些低能量Ga注入的SiN区域可以用作GaN层生长中的成核位点。目前的结果表明，这种方法有可能在任何种类的材料上制备GaN薄膜，只要SiN层能够在它们上形成，从而形成多功能Si器件，并可能取代蓝宝石和SiC衬底的另一种廉价的材料，如Si和玻璃。

As a new method to form hydrogen-free gallium nitride (GaN) thin layers, ion beam direct deposition method under nitrogen ambient was investigated. After 100 eV Ga ion beam was irradiated on a chip of a Si(111) wafer under a nitrogen-radical atmosphere, the composition and the chemical bonding nature of the deposited materials were investigated by X-ray photoelectron spectroscopy (XPS). The XPS spectra of the deposited Ga under nitrogen-radical were very similar to that of an epitaxially grown GaN reference, indicating the possibility of the formation of GaN thin layer using the present method. Because the pure N_2 gas was used as the nitrogen-radical source, no impurity fragments should be incorporated in the deposited materials. As a result, it is shown that the formation of hydrogen-free GaN layers is possible by the present method.In addition, we report the formation of GaN layer at outermost surface of SiN films by using low-energy (60-200 eV) Ga ion irradiation. It is found that the Ga ions were surely implanted in the insulative SiN surface, and the position of the XPS signal of Ga was shifted to 20.2 eV, showing the existence of Ga-N bonds. Because the ion energy used was large enough to break the Si-N bonds, this result shows that the N atoms can be bonded easily with implanted Ga atoms than Si atoms. These low-energy Ga-implanted SiN regions might be used as nucleation sites in the growth of GaN layers. The present result indicates that this method has a potential to fabricate GaN films on any kinds of materials, only if the SiN layer was able to be formed on them, resulting the formation of multifunctional Si devices and the possible substitution of sapphire and SiC substrates to another low-priced materials such as Si and glass.