Stress-modulated composition in the vicinity of dislocations in nearly lattice matched AlxIn1-x N/GaN heterostructures: A possible explanation of defect insensitivity
Stress-modulated composition in the vicinity of dislocations in nearly lattice matched AlxIn1-x N/GaN heterostructures: A possible explanation of defect insensitivity
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DOI：
10.1103/physrevb.83.195309
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发表时间：
2011-05-09
影响因子：
3.7
通讯作者：
Stadelmann, Pierre
中科院分区：
文献类型：
--
作者：
Mouti, Anas;Rouviere, Jean-Luc;Stadelmann, Pierre
通过z衬度成像、应变测量和AlxIn 1-x N/GaN异质结构中的能量色散X射线光谱，提供了在从原子距离到数十纳米的尺度上围绕螺纹位错的成分波动的证据。边缘型位错的原子核环位于高度反对称的元素环境中，而混合位错的富铟坑中心位于原子核环的拉伸侧。观察到的纯刃位错周围的成分波动进行了比较，与弹性静力学自由能模型计算和一个很好的定性和定量的协议。流体静力应力被证明是他们的主要原因：拉伸应力区是铟丰富和压缩应力区是铝丰富。我们表明，混合位错的应力场可以影响合金的组成超过一百纳米远离其核心。铟芯偏析纯螺旋螺纹位错也证明和解释的模型，剪切应力也预计会影响组合物。此外，线程位错显示弯曲在AlxIn 1-xN合金比在GaN，这表明它们是“钉扎”的应力诱导的波动。这种浓度调制可对通常含有高位错密度（在10（8）至10（10）cm（-2）范围内）的III族氮化物器件的光学和电学性质具有重要影响。我们认为应力诱导的成分调制可能是含铟氮化物三元合金缺陷不敏感性的起源。
Evidence of composition fluctuations around threading dislocations at scales ranging from atomic distances to tens of nanometers is provided by z-contrast imaging, strain measurement, and energy dispersive x-ray spectroscopy in AlxIn1-x N/GaN heterostructures. The atomic core rings of edge-type dislocations are shown to lie across highly antisymmetric elemental environments, and the indium-rich pit centers of mixed dislocation are found to lie on the tensile side of their atomic core ring. The observed composition fluctuations around pure-edge dislocations are compared with an elastostatic free energy model calculation and a good qualitative and quantitative agreement is obtained. Hydrostatic stress is shown to be their principal cause: Tensile stress regions are indium rich and compressive stress regions are aluminum rich. We show that the stress field of a mixed dislocation can impact the composition of the alloy more than a hundred nanometers away from its core. Indium core segregation on pure-screw threading dislocation is also evidenced and explained by the model, as shear stress is also expected to affect composition. Furthermore, threading dislocations are shown to bend less in the AlxIn1-x N alloy than in GaN, suggesting that they are "pinned" by stress-induced fluctuations. Such concentration modulations can have an important impact on optical and electrical properties of Group-III nitride devices that generally contain a high dislocation density (in the 10(8) to 10(10) cm(-2) range). We propose that stress-induced composition modulation could be the origin of defect insensitivity in indium-containing nitride ternary alloys.