Defect-rich GaN interlayer facilitating the annihilation of threading dislocations in polar GaN crystals grown on (0001)-oriented sapphire substrates
Defect-rich GaN interlayer facilitating the annihilation of threading dislocations in polar GaN crystals grown on (0001)-oriented sapphire substrates
复制标题
DOI：
10.1063/1.5092284
复制
发表时间：
2019-08
影响因子：
3.2
通讯作者：
M. Barchuk;M. Motylenko;T. Schneider;M. Förste;C. Röder;A. Davydok;S. Lazarev;C. Schimpf;C. Wüstefeld;O. Pätzold;D. Rafaja
中科院分区：
文献类型：
--
作者：
M. Barchuk;M. Motylenko;T. Schneider;M. Förste;C. Röder;A. Davydok;S. Lazarev;C. Schimpf;C. Wüstefeld;O. Pätzold;D. Rafaja
微结构缺陷之间的相互作用被认为是降低缺陷密度和提高晶体质量的可能工具。在本研究中，这一一般的方法被应用于降低高温气相外延直接在(0001)取向的蓝宝石衬底上生长的GaN晶体中的线状位错密度。所研究的GaN晶体是在不同的工艺温度、生长速度和氨气流量下分三步沉积的。第一层GaN适应了蓝宝石和氮化镓之间的晶格失配。因此，它包含大量随机分布的丝位错。下一层GaN是内部结构的，富含缺陷，它弯曲和聚集这些位错，并促进它们的湮灭。最上层的GaN层主要包含簇状线位错，终止了大面积几乎无缺陷的GaN。为了能够可视化和量化三明治状结构各个部分的微结构变化，用纳米聚焦同步辐射衍射、共聚焦显微拉曼光谱和透射电子显微镜对样品进行了研究。透射电子显微镜提供了有关微结构缺陷的种类及其相互作用的信息。同步加速器衍射和显微拉曼光谱揭示了位错密度和晶格参数的深度分布，微结构缺陷之间的相互作用被认为是降低缺陷密度和提高晶体质量的可能工具。在本研究中，这一一般的方法被应用于降低高温气相外延直接在(0001)取向的蓝宝石衬底上生长的GaN晶体中的线状位错密度。所研究的GaN晶体是在不同的工艺温度、生长速度和氨气流量下分三步沉积的。第一层GaN适应了蓝宝石和氮化镓之间的晶格失配。因此，它包含大量随机分布的丝位错。下一层GaN是内部结构的，富含缺陷，它弯曲和聚集这些位错，并促进它们的湮灭。最上层的GaN层主要包含簇状线位错，终止了大面积几乎无缺陷的GaN。为了能够可视化和量化各个部件的微观结构变化。
The interaction of microstructure defects is regarded as a possible tool for the reduction of the defect density and improvement of the crystal quality. In this study, this general approach is applied to reduce the density of threading dislocations in GaN crystals grown using high-temperature vapor phase epitaxy directly on (0001)-oriented sapphire substrates. The GaN crystals under study were deposited in three steps with different process temperatures, growth rates, and ammonia flows. The first GaN layer accommodates the lattice misfit between sapphire and gallium nitride. Thus, it contains a high number of randomly distributed threading dislocations. The next GaN layer, which is internally structured and defect-rich, bends and bunches these dislocations and facilitates their annihilation. The uppermost GaN layer mainly contains bunched threading dislocations terminating large areas of almost defect-free GaN. In order to be able to visualize and to quantify the microstructure changes in individual parts of the sandwich-like structure, the samples were investigated using nanofocused synchrotron diffraction, confocal micro-Raman spectroscopy, and transmission electron microscopy. The transmission electron microscopy provided information about the kind of microstructure defects and their mutual interaction. The synchrotron diffraction and the micro-Raman spectroscopy revealed the depth profiles of dislocation density and lattice parameters.The interaction of microstructure defects is regarded as a possible tool for the reduction of the defect density and improvement of the crystal quality. In this study, this general approach is applied to reduce the density of threading dislocations in GaN crystals grown using high-temperature vapor phase epitaxy directly on (0001)-oriented sapphire substrates. The GaN crystals under study were deposited in three steps with different process temperatures, growth rates, and ammonia flows. The first GaN layer accommodates the lattice misfit between sapphire and gallium nitride. Thus, it contains a high number of randomly distributed threading dislocations. The next GaN layer, which is internally structured and defect-rich, bends and bunches these dislocations and facilitates their annihilation. The uppermost GaN layer mainly contains bunched threading dislocations terminating large areas of almost defect-free GaN. In order to be able to visualize and to quantify the microstructure changes in individual parts...