半导体结构中局域弹性应变场的电子背散射衍射分析

采用扫描电镜中的电子背散射衍射（Electron Backscattering Diffraction,EBSD）技术,对硼掺杂的可动悬空硅薄膜和用于激光二极管（LED）的蓝宝石衬底上异质外延生长GaN层中的弹性应变区进行了测量.将菊池图的图像质量（IQ）和Hough转变强度,以及小角度晶界错配的统计数据作为应力敏感参数,研究了单晶材料系统中,微米～亚微米尺度的晶格畸变状态及局域弹性应变场.EBSD测试获得了硅薄膜窗口区域及LED的GaN外延层中的弹性应变分布.     

蓝宝石上横向外延GaN薄膜

在蓝宝石衬底上利用金属有机物气相外延(MOCVD)方法对横向外延(ELO)GaN薄膜的生长条件进行了研究.在蓝宝石衬底上利用化学腐蚀的方法刻饰出图案,再沉积低温GaN缓冲层作为外延层的子晶层,以降低外延层与衬底的晶格失配与热失配,制备出低位错密度的GaN外延层.分别利用X射线衍射、原子力显微镜及湿法腐蚀对外延层进行检测.     

GaN外延结构中微区应变场的测量和评价

 采用电子背散射衍射(EBSD)技术,测量GaN/蓝宝石结构中的弹性应变场.将EBSD菊池衍射花样的图像质量IQ值及小角度错配作为应力敏感参数,表征GaN-Buffer层-蓝宝石结构中的晶格畸变和转动,显示微区弹性应变场.在GaN/蓝宝石系统中,弹性应变的影响范围大约200×700nm.采用快速傅立叶变换(FFT)提取菊池花样的衍射强度,识别GaN外延结构中的应变/无应变区域.     

蓝宝石上横向外延GaN薄膜

在蓝宝石衬底上利用金属有机物气相外延(MOCVD)方法对横向外延(ELO)GaN薄膜的生长条件进行了研究.在蓝宝石衬底上利用化学腐蚀的方法刻饰出图案,再沉积低温GaN缓冲层作为外延层的子晶层,以降低外延层与衬底的晶格失配与热失配,制备出低位错密度的GaN外延层.分别利用X射线衍射、原子力显微镜及湿法腐蚀对外延层进行检测.     

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.     

GaN外延用蓝宝石衬底的图形化研究进展

因蓝宝石具有良好的稳定性能,且其生产技术成熟,是目前异质外延GaN应用最广泛的衬底材料之一.采用图形化蓝宝石衬底技术可以降低GaN外延层材料的位错密度,提高LED的内量子效率,同时提高LED出光效率提高,近年来引起了国内外的广泛关注.概述了图形化蓝宝石衬底的研究进展,包括图形化蓝宝石衬底的制备工艺、图形尺寸、图形形状及图形化蓝宝石衬底的作用机理;详细介绍了凹槽状、圆孔状、圆锥形、梯形和半球状5种图形形状,并分析了GaN材料在不同图形形状的图形化蓝宝石衬底上的生长机理及不同图形形状对GaN基LED器件性能的影响.对图形化蓝宝石衬底技术的研究方向进行了展望,提出了亟待研究和解决的问题.     

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.     

GaN缓冲层上低温生长AIN单晶薄膜

采用电子回旋共振等离子体增强金属有机物化学气相沉积（ECR－PEMOCVD）技术，在α－Al2O3（0001）（蓝宝石）衬底上，分别以高纯氮气（N2）和三甲基铝（TMAl）为氮源和铝源低温生长氮化铝（AlN）薄膜。利用反射高能电子衍射（RHEED）、原子力显微镜（AFM）和X射线衍射（XRD）等测量样品，研究了AlN缓冲层和氮化镓（GaN）对六方AlN外延层质量的影响，实验表明在GaN缓冲层上能够低温生长出C轴取向的AlN单晶薄膜。     

MOCVD外延生长高阻GaN薄膜材料

采用MOCVD技术在非有意掺杂的条件下，在C面蓝宝石衬底上制备出了高阻的GaN单晶薄膜样品. 用扫描电子显微镜和原子力显微镜分析样品显示GaN外延膜的表面十分平整，表面粗糙度仅有～0.3nm. 样品的X射线双晶衍射摇摆曲线（0002）峰的半峰宽为5.22′，证实所生长的GaN外延层具有较好的结晶质量. 变温Hall测量发现样品的室温电阻率高达6.6e8Ω·cm, 250℃下的电阻率约为10.6Ω·cm.     

反应溅射法沉积氧化铈过渡层研究

采用直流磁控反应溅射法在双轴织构的镍钨合金(Ni-5%W)基带上生长CeO2过渡层。研究了沉积温度、退火时间、水分压等工艺参数对CeO2薄膜取向的影响,并获得了生长高度双轴织构薄膜的优化工艺条件。X射线面内(Φ)扫描揭示了“[100]CeO2∥[110]Ni-W”的单一外延取向关系,原子力显微镜观察到薄膜在退火处理后表面更加平整、致密。     

EBSD技术在第二代高温超导涂层导体研究中的应用

本文利用EBSD技术研究涂层导体用的第二代高温超导镍钨合金基带的显微组织、平均晶粒尺寸、各织构组分含量、取向差分布和特殊晶界(CSL)等。并通过EBSD技术获得缓冲层的显微组织、旋转立方织构含量。     

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.     

EBSD技术在第二代高温超导涂层导体研究中的应用

本文利用EBSD技术研究涂层导体用的第二代高温超导镍钨合金基带的显微组织、平均晶粒尺寸、各织构组分含量、取向差分布和特殊晶界(CSL)等.并通过EBSD技术获得缓冲层的显微组织、旋转立方织构含量.     

Effects of Substrate Pretreatment Conditions on Quality of GaN Epilayer

The pure cubic GaN(c-GaN) has been grown on (001) GaAs substrates by ECR-PAMOCVD technique at low temperature using TMGa and high pure N2 as Ga and N sources,respectively.The effects of substrate pretreatment conditions on quality of cubic GaN epilayer are investigated by the measurements of TEM and XRD.It is found that hydrogen plasma cleaning,nitridation and buffer layer growth are very important for quality of cubic GaN epilayer.     

Effect of AlN buffer thickness on GaN epilayer grown on Si(1 1 1)

We studied the influence of high temperature AlN buffer thickness on the property of GaN film on Si (1 1 1) substrate. Samples were grown by metal organic chemical vapor deposition. Optical microscopy, atomic force microscopy and X-ray diffraction were employed to characterize the samples. The results demonstrated that thickness of high temperature AlN buffer prominently influenced the morphology and the crystal quality of GaN epilayer. The optimized thickness of the AlN buffer is found to be about 150 nm. Under the optimized thickness, the largest crack-free range of GaN film is 10 mm×10 mm and the full width at half maximum of GaN (0 0 0 2) rocking curve peak is 621.7 arcsec. Using high temperature AlN/AlGaN multibuffer combined with AlN/GaN superlattices interlayer we have obtained 2 μm crack-free GaN epilayer on 2 in Si (1 1 1) substrates.     

MOCVD生长中利用Al双原子层控制和转变 GaN的极性

讨论了采用MOCVD在Al2O3衬底上生长GaN过程中的极性问题,在氮化衬底上生长低温缓冲层前沉积一Al层来改变外延层的极性,并用CICISS来测量这一级性,最后给出了一种模型来解释这一极性的转变。     

The role of the low temperature buffer layer and layer thickness in the optimization of OMVPE growth of GaN on sapphire

In agreement with previous work,¹² a thin, low temperature GaN buffer layer, that is used to initiate OMVPE growth of GaN growth on sapphire, is shown to play a critical role in determining the surface morphology of the main GaN epilayer. X-ray analysis shows that the mosaicity of the main GaN epilayer continues to improve even after several μm of epitaxy. This continuing improvement in crystal perfection correlates with an improvement in Hall mobility for thicker samples. So far, we have obtained a maximum mobility of 600 cm²/V-s in a 6 μm GaN epilayer. Atomic force microscopy (AFM) analysis of the buffer layer and x-ray analysis of the main epilayer lead us to conclude that the both of these effects reflect the degree of coherence in the main GaN epitaxial layer. These results are consistent with the growth model presented by Hiramatsu et al., however, our AFM data indicates that for GaN buffer layers partial coherence can be achieved during the low temperature growth stage.     

MOCVD Growth of Device—quality GaN on Sapphire

An AIN Layer grown by an ALE has been developed to improve the growth quality of GaN ON Al2O3 substrate by low-pressure metalorganic vapor phase epitaxy(LP-MOVPE).An ALE AIN layer grown on Al2O3 substrate has a high quality and the structure is similar to GaN, this AIN layer can release the stress between Al2O3 substrate and GaN epilayer.By using this method, the orientation of substrate is extended to GaN epilayer, and the column tilt and the twist are improved, so as to obtain the device-quality GaN.     

EBSD measurements of elastic strain fields in a GaN/sapphire structure

An elastic strain field of the heteroepitaxial GaN layer grown on the sapphire substrate, containing a buffer interlayer, was measured using the electron backscatter diffraction (EBSD). Pattern qualities, Hough transforms and small misorientations of Kikuchi bands on EBSD patterns, as strain sensitive parameters and referred to diffraction intensities, were performed to evaluate the elastically distorted region within the sample. The elastic strain gradient parallel to the growth direction of GaN epilayers was mapped and a strain range from 100 nm to 200 nm was detected.