金属缓冲层上生长GaN薄膜的结构、发光性能及其生长机理

为了解决硅衬底与GaN之间的晶格失配和热失配问题,实验尝试采用常压化学气相沉积法(APCVD),分别以金属镓(Ga)和氨气(NH3)为镓源和氮源,在加入A1、Au/Al两种金属缓冲层和不加缓冲层的硅衬底上生长氮化镓(GaN)薄膜.采用高分辨X射线衍射仪(HRXRD)、X-ray能谱仪(EDS)、场发射扫描电子显微镜(F...     

阳极氧化铝作缓冲层的Si基GaN生长

尝试了Si基上生长GaN外延层的一种新的缓冲层材料一阳极氧化铝，在Si（111）衬底上电子束蒸发铝膜，经阳极氧化后放入MOCVD系统中退火，然后进行GaN外延生长，对材料的微结构和电学性质进行了测量和分析，并将得到的GaN材料制备成光导型的紫外光电探测器，器件在330－380nm紫外光区域有明显的响应，最后响应度为3．5A／W（5V偏压）。     

GaN基底上集成介电薄膜材料的生长方法研究

将以极化为特征、具有丰富功能特性的介电氧化物材料通过外延薄膜的方式,在半导体GaN上制备介电氧化物/GaN集成薄膜,其多功能一体化与界面耦合效应可推动电子系统单片集成化的进一步发展。然而,由于2类材料物理、化学性质的巨大差异,在GaN上生长介电薄膜会出现严重的相容性生长问题。采用激光分子束外延技术(LMBE),通过弹性应变的TiO2的缓冲层来减小晶格失配度,降低介电薄膜生长温度,控制界面应变释放而产生的失配位错,提高了介电薄膜外延质量;通过低温外延生长MgO阻挡层,形成稳定的氧化物/GaN界面,阻挡后续高温生长产生的扩散反应;最终采用TiO2/MgO组合缓冲层控制介电/GaN集成薄膜生长取向、界面扩散,降低集成薄膜的界面态密度,保护GaN半导体材料的性能。所建立的界面可控的相容性生长方法,为相关集成器件的研发提供了一条可行的新途径。     

Si衬底上横向外延GaN材料的微结构和光学性质的研究

用氢化物气相外延 (HVPE)方法在Si(III)衬底上成功横向外延生长出晶体质量较好的GaN薄膜材料。透射电子显微镜 (TEM )的研究结果表明 ,横向外延区域GaN的位错密度明显减小。由于SiO2 掩膜腐蚀角的不同 (分别为 90°和 6 6°) ,导致了横向外延GaN材料一些独特的微观形貌。微区拉曼光谱由数百条拉曼散射曲线组成 ,每一条曲线有三个振动模 ,分别对应Si振动模式 (5 2 0cm- 1) ,E2 模式 (5 6 6cm- 1)和E1(LO)模式(732cm- 1)。在垂直条纹方向 ,峰位和峰宽没有明显的变化 ,而峰强约 5 μm会发生周期性变化     

LPCVD法在GaN上生长Ge薄膜及其特性

本文报道了在GaN/蓝宝石作衬底生长Ge薄膜材料的外延生长及其特性研究。研究了不同外延生长条件。结果表明,使用低压化学气相外延技术在GaN/蓝宝石衬底复合衬底上可以生长Ge薄膜。高分辨X射线衍射谱研究得到了峰位分别位于2θ=27.3°、2θ=45.3°和2θ=52.9°的Ge峰.原子力显微镜研究表明得到的Ge薄膜的表面粗糙度为43.4nm。扫描电子显微镜研究表明生长的Ge/GaN/蓝宝石具有清晰的层界,表面Ge晶粒致密并且分布均匀。Raman谱表明所生长的Ge的TO声子峰位于299.6cm-1,这表明了生长的Ge薄膜具有良好的质量。     

用于Si基片上外延BST薄膜的缓冲层的研究进展

由于界面之间的扩散,很难取得在Si基片上BST薄膜的外延.在这种异质结之间,稳定的缓冲层起着良好的阻挡作用以及结构上的延伸功能.综述了用于外延BST薄膜的缓冲层材料的意义和要求,及国内外通过缓冲层来控制界面以及薄膜的外延取向而获得高质量薄膜的最新研究动态,展望了今后用于外延BST薄膜的缓冲层材料发展的趋势.     

GaN薄膜的研究进展

由于GaN薄膜有希望应用在紫外或蓝光发光器件、探测器以及高速场效应晶体管、高温电子器件,GaN材料是当前研究的一个焦点。本文简要介绍了GaN薄膜的制备、衬底选择、掺杂、缓冲层、发光机制和表征等方面的最新进展。指出GaN材料进一步发展需要解决的关键技术问题。     

硅基GaN外延层的SIMS及XPS研究

采用真空反应法在硅基上制备出了GaN外延层。利用二次离子质谱和X射线光电子能谱对GaN外延层进行了深度剖析和表面分析。结果表明 ,外延层中Ga和N分布均匀 ;在表面处Ga发生了偏聚 ;外延层中还存在Si,O等杂质 ,但这些并未影响到GaN外延层的物相及发光性能。实验还表明 ,在外延生长前采用原位清洗可去除Si衬底表面的氧     

硅衬底GaN基LED研究进展

由于硅具有价格低、热导率高、大直径单晶生长技术成熟等优势以及在光电集成方面的应用潜力,GaN/Si基器件成为一个研究热点.然而,GaN与Si之间的热失配容易引起薄膜开裂,这是限制LED及其它电子器件结构生长的一个关键问题.近年来,随着工艺的发展,GaN晶体质量得到大幅度的提高.同时不少研究小组成功地在Si衬底上制造出LED.介绍了GaN薄膜开裂问题及近期硅衬底GaN基LED的研究进展.     

采用Al缓冲层在蓝宝石衬底上合成GaN多晶薄膜

采用CVD法以金属镓(Ga)和氨气(NH3)为原料,在镀有Al膜的蓝宝石衬底上成功地制备了GaN多晶薄膜。采用高分辨X射线衍射仪(HRXRD)、场发射电子扫描电镜(FESEM)、原子力显微镜(AFM)和光致发光能谱(PL)对样品进行了成分、形貌、表面粗糙度和发光性能分析。结果表明,制备的GaN薄膜为结晶性较好的六方纤锌矿GaN多晶薄膜,用266nm的激光作为激发光源时,光致发光谱中除出现354nm的近带边发射峰外,同时还观察到中心波长位于530nm附近的黄光发光峰及中心波长位于约637nm的红光发光峰。     

Fabrication of GaN epitaxial thin film on InGaZnO4 single-crystalline buffer layer

Epitaxial (0001) films of GaN were grown on (111) YSZ substrates using single-crystalline InGaZnO₄ (sc-IGZO) lattice-matched buffer layers by molecular beam epitaxy with a NH₃ source. The epitaxial relationships are (0001)_GaN//(0001)_IGZO//(111)_YSZ in out-of-plane and [112¯0]_GaN//[112¯0]_IGZO//[11¯0]_YSZ in in-plane. This is different from those reported for GaN on many oxide crystals; the in-plane orientation of GaN crystal lattice is rotated by 30° with respect to those of oxide substrates except for ZnO. Although these GaN films showed relatively large tilting and twisting angles, which would be due to the reaction between GaN and IGZO, the GaN films grown on the sc-IGZO buffer layers exhibited stronger band-edge photoluminescence than GaN grown on a low-temperature GaN buffer layer.     

用于GaN基发光二极管的蓝宝石图形衬底制备进展

近几年, 图形化蓝宝石衬底因其作为GaN基发光二极管外延衬底, 不仅能降低GaN外延薄膜的线位错密度, 还能提高LED的光提取效率而引起国内外许多科研机构的广泛研究兴趣. 本文综述了图形化蓝宝石衬底提高GaN基发光二极管性能的作用机理, 重点评述了目前图形化蓝宝石衬底的制备方法(湿法刻蚀、干法刻蚀、固相反应)和图形尺寸(微米图形化、纳米图形化), 分析比较了不同制备方法和图形尺寸制备蓝宝石图形衬底对GaN基发光二极管性能改善, 最后针对蓝宝石图形衬底制备存在的问题对其今后的发展方向做出展望.     

ECR-MOCVD方法GaN单晶薄膜生长热力学分析

基于热力学平衡和化学平衡理论，针对电子回旋共振金属有机化学气相沉积(ECR-MOCVD)系统生长GaN的特点，给出了化学平衡模型和理论分析结果。计算得出了六方GaN的生长驱动力△P与生长条件(Ⅲ族源输入分压PGa^0、V／Ⅲ比、生长温度)的关系。发现在600—900℃内GaN沉积生长速率由Ⅲ族源气体的质量输运所控制。计算得到了六方GaN生长的决定因素和相图。理论计算和实验结果通过比较发现是吻合的。     

Si Complies with GaN to Overcome Thermal Mismatches for the Heteroepitaxy of Thick GaN on Si

Heteroepitaxial growth of lattice mismatched materials has advanced through the epitaxy of thin coherently strained layers, the strain sharing in virtual and nanoscale substrates, and the growth of thick films with intermediate strain‐relaxed buffer layers. However, the thermal mismatch is not completely resolved in highly mismatched systems such as in GaN‐on‐Si. Here, geometrical effects and surface faceting to dilate thermal stresses at the surface of selectively grown epitaxial GaN layers on Si are exploited. The growth of thick (19 µm), crack‐free, and pure GaN layers on Si with the lowest threading dislocation density of 1.1 × 10⁷ cm^?2 achieved to date in GaN‐on‐Si is demonstrated. With these advances, the first vertical GaN metal–insulator–semiconductor field‐effect transistors on Si substrates with low leakage currents and high on/off ratios paving the way for a cost‐effective high power device paradigm on an Si CMOS platform are demonstrated     

Deposition of GaN films on (1 1 1) Si substrates by alternate supply of TMG and NH3

GaN films were grown on (1 1 1) Si substrates at 1000 °C by separate admittances of trimethylgallium (TMG) and ammonia (NH₃). To achieve high quality GaN films, the optimization in growth temperature and layer thickness of AlN buffer layer between GaN film and Si substrate is required. Cross-sectional transmission electron microscopic observations of the GaN/(1 1 1)Si samples show a nearly parallel orientation relationship between the (0 0 0 1) planes of GaN film and the (1 1 1) planes of Si substrate. Room temperature photoluminescence spectra of high quality GaN films show a strong near band edge emission and a weak yellow luminescence. The achievement of high quality GaN films on (1 1 1) Si substrates is believed to be attributed to enhancement in surface mobilities of the adsorbed surface species and adequate accommodation of lattice mismatch between high temperature AlN buffer layer and Si substrate.     

Optimization of GaN nucleation layer deposition conditions on sapphire substrates in HVPE system

The influence of deposition conditions of nucleation GaN layer on the properties of high-temperature GaN layer, grown on sapphire substrates, was investigated. The hydride vapor phase epitaxy (HVPE) three-section horizontal hot-wall furnace technique was applied. Various temperatures, HCl flows and time intervals of nucleation layer growth were utilized. Based on previous studies the following experimental conditions were selected: temperature was kept at 450 or 570 °C, and HCl flows were 8 or 10 sccm/min. The duration of nucleation layer deposition was 5, 7 and 9 min. The scanning electron microscopy technique was applied for the investigation of nucleation layer morphology after migration. Thick GaN layers were deposited during the three-step growth process at 1060 °C. Samples with various surface morphologies were obtained. Photoluminescence spectra and X-ray measurements were performed, which permitted clarifications of the influence of growth conditions of the nucleation layer on the properties of high-temperature layers.