A Transmission Electron Microscopy Observation of Dislocations in GaN Grown on (0001) Sapphire by Metal Organic Chemical Vapor Deposition
A Transmission Electron Microscopy Observation of Dislocations in GaN Grown on (0001) Sapphire by Metal Organic Chemical Vapor Deposition
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DOI：
10.1143/jjap.47.7998
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发表时间：
2008-10
影响因子：
1.5
通讯作者：
Shi-yao Huang;J. Yang
中科院分区：
文献类型：
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作者：
Shi-yao Huang;J. Yang
利用透射电子显微镜（TEM）对（0001）蓝宝石衬底上金属有机化学气相沉积（MOCVD）生长的GaN中的位错进行了观察。GaN膜在生长平面中相对于衬底围绕c轴旋转30°。通过TEM分析发现，约3%（或更少）的螺位错为纯螺位错（B =），20%为纯刃位错（B = 1/3）。剩余的77%为混合型位错，即在（0001）蓝宝石衬底上生长的GaN外延层中的主要位错类型为混合型。此外，为了进一步了解GaN/蓝宝石界面上的位错组态，制备了GaN/蓝宝石界面的平面TEM样品。GaN/蓝宝石界面的平面TEM图像揭示了位于界面上的极高密度的扭结位错，位错密度约为8×109 cm-2，涉及高应变和应力。将8×109 cm-2位错密度与GaN自由表面附近的另一个平面TEM图像（6×108 cm-2）进行比较，结果表明，位于衬底上的约7.5%的位错合并为从界面到GaN表面产生的螺旋位错。
A transmission electron microscopy (TEM) observation of dislocations in GaN grown on (0001) sapphire by metal organic chemical vapor deposition (MOCVD) was carried out in this study. The GaN film was rotated 30° around the c-axis in the growth plane against the substrate. The finding of this research, according to TEM analysis, is that about 3% (or less) of the threading dislocations are pure screw (b = ) and 20% are pure edge (b = 1/3 ). The remaining threading dislocations, about 77%, are mixed-type dislocations; that is the major dislocation type in the GaN epitaxial layer grown on (0001) sapphire is the mixed type. In addition, to further understand the dislocation configuration on the interface of GaN/sapphire, a plane-view TEM sample of the GaN/sapphire interface was prepared. The plane-view TEM image of the GaN/sapphire interface reveals an extremely high density of kink dislocations lying on the interface, with a dislocation density of about 8×109 cm-2, involving high strain and stress. A comparison of the 8×109 cm-2 dislocation density with another plane-view TEM image (6×108 cm-2) near the GaN free surface revealed that approximately 7.5% of the dislocations lying on the substrate coalesce into threading dislocations generated from the interface to the GaN surface.