We report on the growth of AlN epilayers at reasonably low temperatures of 1050–1110 °C on non-miscut c-plane sapphire by metal organic chemical vapor deposition (MOCVD). A systematic study of growth parameters revealed that the thickness of the low temperature (LT) nucleation layer (NL) plays a critical role in improving the screw and edge dislocation densities and surface morphology of the AlN epilayer. A surface kinetics based physico-chemical model is proposed to optimize the crystalline quality and is found to correlate well to the experimental observations. Using a 7 nm nominally-thick LT NL, a 0.5 μm thick AlN epilayer with an rms roughness of 0.15 nm, and (002) and (102) omega scan widths of 18 arc sec and 970 arc sec, respectively, was realized. A grain coalescence model for stress generation is used to correlate the change in AlN growth stress with variation in the NL thickness, and it is shown that in-situ stress measurement can be employed as an early signature for reproducibility of the crystalline quality. This study suggests that AlN/sapphire templates can potentially be realized for a reasonably low thickness (0.5 μm) and at temperatures as low as 1050 °C, which is accessible by most of the III-nitride MOCVD systems.

中文翻译：

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AlN 在蓝宝石上的生长：通过表面动力学模型预测最佳成核密度

我们报告了通过金属有机化学气相沉积 (MOCVD) 在 1050-1110°C 的合理低温下在非错切 c 面蓝宝石上生长 AlN 外延层。对生长参数的系统研究表明，低温 (LT) 成核层 (NL) 的厚度在提高 AlN 外延层的螺旋和刃位错密度以及表面形貌方面起着关键作用。提出了一种基于表面动力学的物理化学模型来优化结晶质量，并且发现与实验观察密切相关。使用标称厚度为 7 nm 的 LT NL，实现了 0.5 μm 厚的 AlN 外延层，其均方根粗糙度为 0.15 nm，（002）和（102）Ω 扫描宽度分别为 18 弧秒和 970 弧秒。用于应力生成的晶粒聚结模型用于将 AlN 生长应力的变化与 NL 厚度的变化相关联，并且表明原位应力测量可用作结晶质量再现性的早期特征。这项研究表明，AlN/蓝宝石模板有可能实现相当低的厚度（0.5 μm）和低至 1050 °C 的温度，大多数 III 族氮化物 MOCVD 系统都可以实现这一点。