【作者】 刘亦安；

【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， 2006， 硕士

【摘要】 氮化镓（GaN）是一种前景甚佳的直接宽带隙半导体材料,具有优良的光、电学性质和优异的机械性质及热的稳定性,是当前世界上最为先进的半导体材料之一。它可用作发光二极管,并可用于荧光灯和白炽灯。它还具有光催化剂特性,这使它成为燃料电池的潜在用料。GaN及其合金的带隙覆盖了从红光到紫外的光谱范围,其高亮度发光二极管和激光器一经出现即以惊人的速度实现了商品化,目前GaN广泛应用于制造蓝绿光发光二极管（LED）,激光器（LD）,紫外波段的探测器以及高温大功率集成电路等器件,并且还可作为环保新材料应用于环境保护,成为近年来半导体材料研究的热点,是制作性能优越的光电器件的理想材料。研究表明,GaN粉末在制造光电、大功率、高温电子器件方面的作用正逐渐受到重视,GaN粉末在生长高质量的GaN薄膜和GaN纳米线过程中发挥着源的作用,S.H.Lee等认为GaN粉末的制备在柱状GaN薄膜的生长和纳米尺寸的光学技术的应用等方面正起着越来越重要的作用,另外,GaN粉末本身也可以作为高质量的荧光粉。一般把升华法和高压溶液法认为是合成GaN晶体的有效方法,但是这些方法要求高质量和单相的GaN粉末源作为前体材料。因此直接合成高质量的GaN粉末是当前国际上一项重要研究课题。1993年,P.Millet等采用新颖的热机械合金过程首次合成GaN粉末,但此方法耗时长且得到的粉末纯度不高。1996年,H.D.Li等人报道采用直流等离子弧光法通过Ga与N₂和NH₃的混合气体反应合成超纯GaN粉末,粉末的纯度有所提高,但纯度不易控制且操作复杂。在本文中,主要探索了一种新的两步合成颗粒状GaN粉末的制作途径,即利用溶胶-凝胶和高温氨化二步相结合的方法,利用镓酸三乙脂（Ga（OC₂H₅）₃）作为前驱体形成的Ga₂O₃凝胶作为镓源,以NH₃（99.99%）为氮源,使它们在L4513II-2/QWZ型高温扩散炉中高温氮化20min获得GaN粉末。实验和测试结果表明利用溶胶-凝胶和高温氨化二步法制备GaN粉末的最佳条件与溶胶-凝胶法制备凝胶的不同工艺条件有关。本实验中我们利用Ga（OC₂H₅）₃作为反应前驱物和无水乙醇相混合制备凝胶采用四个不同的配比,即Ga（OC₂H₅）₃和无水乙醇的配比分别为:（1）2:40;（2）2:70;（3）2:100;（4）2:130。实更多还原

【Abstract】 Gallium Nitride (GaN) is an excellent promising direct wide bandgapsemiconductor material and also is one of the most advanced semiconductors in theworld due to its excellent property of light and electrology, its outstanding mechanismpropoty and heat stability. (physics, chemistry , mechanical and heat stability.It can beused for light emitting diodes and also used for fluorescent light lamp or incandescentlamp. In addition, GaN is also appropriate for a potential application of fuel batteries.The spectrum scope from glow to ultraviolet light are overcastted by the band gap ofboth GaN and alloy. The commodity is swiftly realized as soon as the light emittingdiodes and laser came into existence. Up to the present, it can be widely applied tolight emitting devices, such as blue, near ultraviolet, violet light emitting diodes, laserand high temperature / high power microelectronic devices , At the same time, it can beused as a new eco-friendly material and applied into environmental protection. It isbecoming the hotspot for semiconductor materials and also ideal for performancesuperiority of optoelectronic devices. While the research years indicate that theinfluence of GaN powder are gradually being attached much importance to the aspectof fabricating of photoelectricity、high temperature and high power microelectronicdevices, and also exerts a function of origination in the course of developing highqulity GaN films or GaN nanowires, that preparation of GaN powders are exerting anmore and more important affection on the growth of mast GaN films and theapplication of optics technique of nano-dimension considered by S.H.Lee et al,moreover, GaN itself can also serve as fluorescent light powder of high quality..Sublimation and high-pressure solution methods are considered as effective methodsfor crystal growth of GaN. The methods demand the availability of well-characterizedGaN powder source with high purity and signal phase. So considerable effort has beendirected towards the synthesis of highly-qualified GaN powders. In 1993, GaNpowders have been synthesized for the first time by a novel hot mechanical alloyingprocess by P. Millet et al, but this method is time-consuming and can only get GaNpowder of low purity. In 1996, ultra-pure GaN powders have also been synthesized bythe direct current arc plasma method by H.D.Li et al, using Ga、both mixture of N2 andNH3 as reaction material, but the increase of purity can not make up theuncontrollability and complication in the operation.In this dissertation, a novel two-step method of synthesizing GaN powder ischiefly discussed, By means of a two-step combination of sol-gel process withhigh–temperature ammoniating , gallium oxide (Ga2O3) gel formed by usingGa(OC2H5)3 as a new precursor are used as the gallium source, and ammonia(99.99%)is used as the nitrogen source, GaN powders are synthesized by nitriding Ga2O3 gel inthe flow of NH3 gas at different temperature for 20 min.The results of experiment and characterization indicate that the optimal conditionof fabrication of GaN powders using two-step method of sol-gel and high nitridationtemperature is associated with a different technology that gel can be fabricated bysol-gel. In this experiment, four different proportionings are used to fabricate gel bymeans of combination of Ga(OC2H5)3 as precursor with anhydrous C2H5OH, that is tosay, the proportioning of Ga(OC2H5)3 and anhydrous C2H5OH respectively is : (1)2:40;(2)2:70;(3)2:100;(4)2:130 . The results of experiment and characterizationalso indicate that the optimal condition of GaN powders in the two proportioning of(1)2:40 and(2)2:70 synthesized by reactioning gel with the flowing NH3 is 20minat 950℃, however, in the other two proportioning of (3)2:100 and(4)2:130, theoptimal condition of GaN powders synthesized by the reaction of gel with the flowingNH3 is 20min at 1000℃, at the same time, the optimal condition GaN powderssynthesized directly by the reaction β-Ga2O3 with the flowing NH3 that areinvestigated is 20min at 950℃. and all this experiment go along at constant pressure.Measurement results indicate that the synthesised GaN by different conditions is of asingle-phase hexagonl wurtzite structure. In any unintentionally doped sample, C andO are inescapable. When the sample is investigated by XPS, C and O are found, but Ois attributed to chemisorbed oxygen. Blue light emission is as a major peak in PLspectrum, and the emission is attributed to the transition from shallow donor level tothe acceptor carbon. When the morphology of GaN are investigated, the GaN powderssynthesized by this method is a single, short rod-like crystal and its size is about150nm in the two proportioning of (1)2:40 and(2)2:70,otherwise,it is about450nm in the other two proportioning of (1)2:100 and(2)2:130. The influenceson formation、morphology、structure and size of crystal of the same and differentproportioning condition at different nitridation temperature are positively discussed,and the research results indicate that the pattern、surface morphology、size andgranularity of GaN microcrystal under the same nitridation time are influenced bydifferent preparation condition of sol-gel and different nitridation temperature of gel,moreover, the optimal condition of preparation of GaN powders is influenced by thedifferent proportioning of reaction precursor.The mechanism of growth of GaN powder is also studied.The free energy ofreaction Ga2O3 gel and NH3 is positive and, thus, indication that they would not occurin the mechanism of growth studied. The reaction is favorable only if Ga2O is formedin this process. In the course of high nitridation temperature, When nitridationtemperature exceeded 600℃, NH3 is decomposed into NH2, NH, N2, N, H2 and H, so itcan be used as N source and the sample of GaN gel as Ga source. When thetemperature exceed 850℃, Ga2O3 deoxidized by H2 first converts into Ga2O, O2-inGa2O powders is then replaced by N3-. Along with time increases, GaN particles arecoagulated and crystal nuclei are formed, and then large grains are formed gradually.更多还原