Abstract The strain relaxation process of undoped and Si-doped AlxGa1−xN with various compositions and thicknesses on semipolar (2 0 2 ¯ 1) bulk GaN substrate was investigated via the cathodoluminescence (CL) and high-resolution x-ray diffraction (XRD) analyses. CL analyses showed that the strain relaxation occurred through three different mechanisms. At first, the relaxation was initiated by the basal-plane (BP) misfit dislocations (MDs) along [1 1 2 ¯ 0] followed by the crack formation along [1 0 1 ¯ 4] . As the Al composition and/or thickness of AlGaN layer further increased, the crack density saturated and non-basal plane (NBP) MDs almost parallel to [1 0 1 ¯ 4] started emerging due to the prismatic slip. Observed crack spacing was 40–60 μm at which the energy of exposing new surfaces from the cracks is higher than Peierls potential associated with the prismatic slip. By introducing Si (2.0–6.0 × 1018 cm−3) into the film, the formation of both BP and NBP MDs could be suppressed within our growth conditions. However, Si doping was not effective in suppressing the crack formation but there was no significant change of its density either.

中文翻译：

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在 (202¯1) 体 GaN 衬底上生长未掺杂和 Si 掺杂的半极性 AlxGa1-xN 的应变弛豫过程

摘要 通过阴极发光 (CL) 和高分辨率 X 射线衍射 (XRD) 研究了不同成分和厚度的未掺杂和 Si 掺杂的 AlxGa1−xN 在半极性 (2 0 2 ¯ 1) 体 GaN 衬底上的应变弛豫过程。分析。CL 分析表明应变松弛通过三种不同的机制发生。首先，松弛是由沿 [1 1 2 ¯ 0] 的基面 (BP) 错配位错 (MD) 引发的，然后是沿 [1 0 1 ¯ 4] 的裂纹形成。随着AlGaN层的Al成分和/或厚度进一步增加，由于棱柱滑移，几乎平行于[1 0 1 ¯ 4]的裂纹密度饱和和非基面（NBP）MD开始出现。观察到的裂纹间距为 40-60 μm，此时从裂纹中暴露出新表面的能量高于与棱柱滑移相关的 Peierls 势能。通过将 Si (2.0–6.0 × 1018 cm-3) 引入薄膜中，可以在我们的生长条件下抑制 BP 和 NBP MD 的形成。然而，Si掺杂不能有效抑制裂纹形成，但其密度也没有显着变化。