Abstract Droplet Epitaxy of AlGaN nanostructures was investigated in this work. Growth was carried out by Plasma Assisted Molecular Beam Epitaxy (PA-MBE) under extreme group III rich conditions, where the excess metal remained on the growth surface and formed nanoscale metallic droplets due to the interplay of surface energy, surface diffusion and desorption, all of which are strongly dependent on the relative arrival rates of gallium and aluminum and the substrate temperature. Intermittent exposure of this metallic film to active nitrogen forms various types of nanostructures, whose morphology, composition and luminescence properties were evaluated. Our results indicate that for AlN, the droplet epitaxy process forms random arrays of uniform well oriented [0 0 0 1] nanorods with a height of ∼1 µm and a diameter of 250 nm. For AlGaN grown under excess gallium, and intermittent exposure to the active plasma, structures with diameters of 200 µm to 600 µm and a height of 80 nm were observed. We report the spontaneous formation of lateral concentric heterostructures under these conditions. A single photoluminescence (PL) peak was observed at about 260 nm with a room temperature to 4 K intensity ratio of ∼25%.

中文翻译：

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在过量 III 族条件下生长 AlGaN 合金：垂直纳米棒的形成

摘要 本工作研究了AlGaN纳米结构的液滴外延。在极端的 III 族富集条件下，通过等离子体辅助分子束外延 (PA-MBE) 进行生长，由于表面能、表面扩散和解吸的相互作用，多余的金属保留在生长表面并形成纳米级金属液滴，所有其中很大程度上取决于镓和铝的相对到达速率和衬底温度。这种金属薄膜间歇性地暴露在活性氮中会形成各种类型的纳米结构，对其形态、成分和发光特性进行评估。我们的结果表明，对于 AlN，液滴外延过程形成了高度为 ~1 µm 和直径为 250 nm 的均匀良好取向的 [0 0 0 1] 纳米棒的随机阵列。对于在过量镓下生长并间歇性暴露于活性等离子体的 AlGaN，观察到直径为 200 µm 至 600 µm 和高度为 80 nm 的结构。我们报告了在这些条件下横向同心异质结构的自发形成。在约 260 nm 处观察到单个光致发光 (PL) 峰，室温与 4 K 强度比约为 25%。