GaN在Si(001)上的ECR等离子体增强MOCVD直接生长研究

研究了用电子回旋共振(ECR)等离子体增强金属有机物化学气相沉积(PEMOCVD)技术在Si(001)衬底上,低温(620～720℃)下GaN薄膜的直接外延生长及晶相结构.高分辨透射电镜(HRTEM)和X射线衍射(XRD)结果表明:在Si(001)衬底上外延出了高度c轴取向纤锌矿结构的GaN膜,但在GaN/Si(001)界面处自然形成了一层非晶层,其两个表面平坦而陡峭,厚度均匀(≈2nm).分析认为,在初始成核阶段N与Si之间反应所产生的这层SixNy非晶层使GaN的β相没有形成.XRD和原子力显微镜(AFM)结果表明,衬底表面的原位氢等离子体清洗,GaN初始成核及后续生长条件对GaN膜的晶体质量非常重要.     

在复合衬底γ-Al2O3/Si(001)上生长GaN

采用分子束外延(MBE)生长方法,使用γ-Al2O3材料作为新型过渡层,在Si(∞1)衬底上获得了没有裂纹的GaN外延层,实验结果表明使用γ-Al2O3过渡层有效地缓解了外延层中的应力.通过生长并测试分析几种不同结构的外延材料,研究了复合衬底γ-Al2O3/Si(001)生长GaN情况,得到了六方相GaN单晶材料,实现了GaN c面生长.预铺薄层Al及高温AlN层可以提高GaN晶体质量,低温AlN缓冲层可以改善GaN表面的粗糙度.为解决Si(001)衬底上GaN的生长问题提供了有益的探索.     

在复合衬底γ-Al2O3/Si(001)上生长GaN

采用分子束外延(MBE)生长方法,使用γ-Al2O3材料作为新型过渡层,在Si(∞1)衬底上获得了没有裂纹的GaN外延层,实验结果表明使用γ-Al2O3过渡层有效地缓解了外延层中的应力.通过生长并测试分析几种不同结构的外延材料,研究了复合衬底γ-Al2O3/Si(001)生长GaN情况,得到了六方相GaN单晶材料,实现了GaN c面生长.预铺薄层Al及高温AlN层可以提高GaN晶体质量,低温AlN缓冲层可以改善GaN表面的粗糙度.为解决Si(001)衬底上GaN的生长问题提供了有益的探索.     

Si衬底和Si-SiO_2-Si柔性衬底上的GaN生长

使用MBE方法在Si(111)衬底和Si SiO2 Si柔性衬底上生长了GaN外延层 ,并对在两种衬底上生长的样品进行了对比分析 .在柔性衬底上获得了无裂纹的外延层 ,其表面粗糙度为 0 6nm .研究了GaN外延层中的应力及其光学性质 ,光致发光测试结果表明柔性衬底上生长的外延层中应力和杂质浓度明显低于直接生长在Si衬底上的样品的值 .研究结果显示了所用柔性衬底有助于改善GaN外延膜的质量     

Si衬底和Si-SiO2-Si柔性衬底上的GaN生长

使用MBE方法在Si(111)衬底和Si-SiO2-Si柔性衬底上生长了GaN外延层,并对在两种衬底上生长的样品进行了对比分析.在柔性衬底上获得了无裂纹的外延层,其表面粗糙度为0.6nm.研究了GaN外延层中的应力及其光学性质,光致发光测试结果表明柔性衬底上生长的外延层中应力和杂质浓度明显低于直接生长在Si衬底上的样品的值.研究结果显示了所用柔性衬底有助于改善GaN外延膜的质量.     

在复合衬底γ-Al2O3/Si(001）上生长GaN

采用分子束外延（MBE）生长方法，使用γ-Al₂O₃材料作为新型过渡层，在Si(001）衬底上获得了没有裂纹的GaN外延层，实验结果表明使用γ-Al₂O₃过渡层有效地缓解了外延层中的应力. 通过生长并测试分析几种不同结构的外延材料，研究了复合衬底γ-Al₂O₃/Si (001）生长GaN情况，得到了六方相GaN单晶材料，实现了GaN c面生长. 预铺薄层Al及高温AlN层可以提高GaN晶体质量，低温AlN缓冲层可以改善GaN表面的粗糙度. 为解决Si(001）衬底上GaN的生长问题提供了有益的探索.     

Si(111)衬底上生长的GaN的形貌与AlN缓冲层生长温度的关系

利用LP-MOCVD技术在Si(111)衬底上,用不同温度生长AlN缓冲层,再在缓冲层上外延GaN薄膜.采用高分辨率双晶X射线衍射(DCXRD)技术和扫描电子显微镜(SEM)分析这些样品,比较缓冲层生长温度对缓冲层和外延层的影响,并提出利用动力学模型解释这种温度的影响.进一步解释了GaN外延层表面形貌中"凹坑"的形成及"凹坑"与缓冲层生长温度的关系.结果表明,温度的高低通过影响缓冲层初始成核密度和成核尺寸来影响外延层表面形貌.     

SiNx插入层对Si衬底上生长GaN薄膜晶体质量和表面形貌的影响

在Si(111)衬底上采用金属有机化合物化学气相沉积(MOCVD)技术外延生长GaN薄膜,对外延生长所得GaN薄膜的晶体结构和表面形貌进行表征,并研究SiNx插入层对GaN薄膜的晶体质量和表面形貌的影响.结果表明,在Si衬底上生长GaN薄膜过程中引入SiNx插入层可使GaN薄膜的(10-12)面的X-射线回摆曲线的半峰宽(FWHM)值从974.01减小到602.01arcsec;表面凹坑等缺陷减少、表面平整度提高.可见,SiNx插入层对在Si衬底上外延生长GaN薄膜的晶体质量和表面形貌有着重要的影响.     

AlGaN缓冲层结构对Si基GaN材料性能的影响

Si衬底与GaN之间较大的晶格失配和热失配引起的张应力使GaN外延层极易产生裂纹,如何补偿GaN所受到的张应力是进行Si基GaN外延生长面临的首要问题.采用金属有机化合物化学气相沉积(MOCVD)技术在4英寸(1英寸=2.54 cm)Si (111)衬底上制备了GaN外延材料并研究了不同AlGaN缓冲层结构对Si基GaN外延材料性能的影响,并采用高分辨X射线衍射仪(HRXRD)、原子力显微镜(AFM)、喇曼光谱以及光学显微镜对制备的GaN材料的性能进行了表征.采用3层A1GaN缓冲层结构制备了表面光亮、无裂纹的GaN外延材料,其(002)晶面半高宽为428 arcsec,表面粗糙度为0.194 nm.结果表明,采用3层A1GaN缓冲层结构可以有效地降低GaN材料的张应力和位错密度,进而遏制表面裂纹的出现,提高晶体质量.     

Si(001)斜切衬底上Ge量子点的固相外延生长

研究了Si(001)面偏[110]方向6°斜切衬底上Ge量子点的固相外延生长.实验结果表明,在Si(001)6°斜切衬底上固相外延生长Ge量子点的最佳退火温度为640℃,在斜切衬底上成岛生长的临界厚度低于在Si(001)衬底成岛生长的临界厚度,6°斜切衬底上淀积0.7nm Ge即可成岛,少于Si(001)衬底片上Ge成岛所需的淀积量.从Ge量子点的密度随固相外延温度的变化曲线,得到Ge量子点的激活能为1.9eV,远高于Si(111)面上固相外延Ge量子点的激活能0.3eV.实验亦发现,在Si(001)斜切衬底上固相外延生长的Ge量子点较Si(001)衬底上形成的量子点的热稳定性要好.     

Investigation of Co/SiC interface reaction

Interface reaction, phase transition, and composition were investigated for Co thin films on amorphous SiC films as a function of heat treatment (600～1000°C). Amorphous SiC layers were grown on (001) Si substrate by magnetron sputter deposition. The SiC layers had a 1:1 stoichiometric ratio of Si to C and an amorphous structure containing microcrystals. The interface reaction between a sputter-deposited Co (250Å thick) and amorphous SiC (2000Å thick) layer on a (001) Si substrate induced by vacuum annealing at temperatures of 600–1000°C was examined. Co₂Si was formed at 700°C as the first crystalline phase and CoSi at 800°C as the final stable phase of the Co/SiC interface reaction. This phase sequence of Co₂Si→CoSi was interpreted in terms of the effective heat of formation and the calculated ternary Co-Si-C phase diagram, and it was consistent with the experimental results. The high formation temperature of the first crystalline Co₂Si phase and no formation of a final stable CoSi₂ phase are discussed in comparison with Co/Si interface reaction and related to the binding energy of the reacting materials. In addition, the behavior of free carbon remaining after the Co/SiC reaction was investigated. This free carbon moved to the top of the reacted cobalt silicide/SiC layer.     

Low-temperature ECR-PEMOCVD deposition of high-quality crystalline gallium nitride films: A comparative study of intermediate layers for growth on amorphous glass substrates

A low temperature growth method based on an electron cyclotron resonance plasma-enhanced metal organic chemical vapor deposition system (ECR-PEMOCVD) was proposed for the growth of GaN (Gallium nitride) films on ordinary amorphous soda-lime glass substrates. To alleviate the large lattice mismatch between GaN film and glass substrate and improve the heat dissipation performance for potential optoelctrical device application, five intermediate layers (Cu, Ni, Ti, Ag, and ITO) were deposited on the glass substrate before the growth of GaN. A comparative study was performed through structural analysis of the as-grown GaN films with various intermediate layers investigated by means of in-situ reflection high energy electron diffraction (RHEED), X-ray diffraction (XRD), and atomic force microscopy (AFM). The results indicate that the Ti intermediate layer has a great advantage over other intermediate layers in view of crystalline quality and smooth surface, therefore is more suitable and preferred for the potential application in optoelectronic devices.     

Growth of thick gan films on rf sputtered ain buffer layer by hydride vapor phase epitaxy

High crystalline quality thick GaN films were grown by vapor phase epitaxy using GaCl₃ and NH₃. The growth rate was in the range of 10~15 Μm/h. GaN films grown at higher temperatures (960~ 1020?C) were single crystalline with smooth surface morphologies. No chlorine impurity was incorporated in these films during growth. The best crystalline quality and surface morphology of grown films was achieved by sputtering a thin A1N buffer layer, prior to growth. According to reflection high energy electron diffraction and atomic force microscopy measurements, as-sputtered A1N buffer layer was amorphous with root means square roughness of 0.395 nm and then crystallized during the GaN growth. This improved the GaN growth due to more uniform distribution of GaN nucleation. Rutherford backscattering channeling experiments produced the lowest value from the GaN film grown on a-Al₂O₃ with a 500å A1N buffer layer at 1020?C.     

Low temperature annealing behaviors of the titanium films formed by the ionized sputtering process on (001) silicon substrates

We investigated the low temperature reactions between the Ti films created by the ionized sputtering process and the (001) single crystal silicon wafers using high resolution transmission electron microscopy and x-ray diffractometry. We observed that the amorphous Ti-Si intermixed layer is formed at the Ti-Si interface whose thickness increased with the thickness of the deposited Ti films. The amorphous interlayer grew upon annealing treatments at the temperatures below 450°C. We also observed that the crystallization of the amorphous interlayer occurred upon annealing at 500°C. The first formed phase is Ti₅Si₃ in contact with Ti films, which is epitaxial with Ti films. Upon further annealing at 500°C, the Ti₅Si₄ phase and C49 TiSi₂ phase formed in the regions close to Ti films and Si substrates, respectively.     

非晶态SiO2过渡层对生长C轴取向LiNbO3薄膜的影响

采用磁控溅射方法,在Si衬底和LiNbO3薄膜之间引入SiO2过渡层制备LiNbO3薄膜。采用X射线衍射（XRD〉、傅里叶变换红外吸收光谱（FT-IR）和扫描电子显微镜（SEM）对LiNbO3薄膜的结晶取向、组成成分和表面形貌进行了表征,重点研究了非晶态SiO2过渡层对LiNbO3薄膜C轴取向的影响。结果表明,非晶态S...     

热壁化学汽相沉积Si基GaN奇异面

利用热壁化学汽相沉积在Si基上生长GaN薄膜。用扫描电镜(SEM)、选择区电子衍射(SAED)、X射线衍射(XRD)、傅里叶红外透射谱(FTIR)和荧光光谱(PL)对样品进行形貌、结构、组分和发光特性的分析。SEM显示在平滑的表面上出现了由绳状、树根状、项链状晶体组成的奇异面。FTIR、XRD和SAED显示生成的GaN奇异面呈六方纤锌矿多晶结构同时含有少量的碳污染。PL谱显示了不同于一般GaN发光谱的发光峰。     

多孔硅外延转移技术制备以氮化硅为绝缘埋层的SOI新结构

为减少自加热效应 ,利用多孔硅外延转移技术成功地制备出一种以氮化硅为埋层的 SOI新结构 .高分辨率透射电镜和扩展电阻测试结果表明得到的 SOI新结构具有很好的结构和电学性能 ,退火后的氮化硅埋层为非晶结构 .     

Nanoscale spatial phase modulation of GaN on a V-grooved Si Substrate-cubic phase GaN on Si(001) for monolithic integration

Nanoscale spatial phase modulation of GaN grown on a 355-nm period array of V-grooves fabricated in a Si(001) substrate is reported. Orientation-dependent selective nucleation of GaN in metal-organic vapor phase epitaxy begins from the opposing Si{111} sidewalls and rapidly fills each V-groove. At the initial stages of growth, the GaN deposited on the sidewalls has hexagonal phase with the c-axis normal to the Si{111}. As the growth continues, the filling of the V-groove over these misaligned hexagonal phase regions results in a transition to a cubic phase with its principal crystal axes parallel to those of the Si substrate. In a cross-sectional view perpendicular to the grooves, the defected hexagonal phase region and the clean cubic phase region above it form a boundary at the inside of each V-groove which is parallel to the Si{111} sidewalls. The GaN surface is almost planarized for only 75-nm deposition and is parallel to the original [001] plane of the Si substrate. The GaN clearly exhibits nanoscale spatial phase modulation with a periodic separation of hexagonal and cubic crystal structures across the groove direction for 600-nm deposition, implying a possibility of cubic phase GaN on an isolated single V-groove fabricated in a Si(001) substrate for monolithic integration. The structural/optical properties and stress measurements of this phase-modulated GaN grown on a nanoscale faceted Si surface are presented.     

Si衬底GaN基多量子阱外延材料的TEM研究

本文采用高分辨透射电子显微技术对在Si衬底生长的GaN基多量子阱外延材料的位错特征、外延层与衬底的晶体取向关系及界面的结晶形态等微观结构进行了分析和研究.结果表明:Si衬底生长的GaN与衬底有一定的取向关系;材料在MQW附近的穿透位错密度达108 cm-2量级,且多数为刃型位错;样品A的多量子阱下方可见平行于界面方向的...