Abstract The formation mechanism of Ga-rich streaks in the AlGaN layers formed at macro-step edges was investigated by analyzing AlGaN layers grown by metalorganic vapor phase epitaxy on AlN/sapphire-templates. Energy dispersive X-ray spectroscopy in the cross-sectional scanning transmission electron microscopy revealed that the macro-steps formed during AlN growth were maintained through the upper AlGaN layer. This can be explained by the less interaction between adjacent macro-steps due to the sufficiently smaller surface diffusion lengths of Ga and Al species than the inter-macro-step distance of submicron to a few microns. Moreover, atomic force microscopy indicated that the apparent smooth region between macro-steps involved many atomic steps and terrace width of a few ten nanometers which may be the actual scale of the diffusion lengths. At the macro-step edge, facets that are different from a c-plane are formed. The higher incorporation efficiency of Ga atoms on these facets compared with that of the c-plane likely led to the formation of Ga-rich streaks due to the less inter-surface diffusion between the facets and c-plane regions. We demonstrated AlGaN growth without Ga-rich streaks using the flattened AlN/sapphire-template by polishing; this resulted in the achievement of homogeneous emission energies in AlGaN-based quantum wells.

中文翻译：

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在 AlN/蓝宝石模板上生长 AlGaN 的宏观台阶边缘富 Ga 条纹的形成机制和抑制

摘要 通过分析在AlN/蓝宝石模板上通过金属有机气相外延生长的AlGaN 层，研究了在宏观台阶边缘形成的AlGaN 层中富Ga 条纹的形成机制。横截面扫描透射电子显微镜中的能量色散 X 射线光谱显示，在 AlN 生长过程中形成的宏观台阶通过上层 AlGaN 保持。这可以解释为由于 Ga 和 Al 物质的表面扩散长度比亚微米到几微米的宏步间距离足够小，因此相邻宏步之间的相互作用较少。此外，原子力显微镜表明，宏观台阶之间的明显平滑区域涉及许多原子台阶和几十纳米的平台宽度，这可能是扩散长度的实际尺度。在宏台阶边缘，形成不同于 c 平面的刻面。由于小平面和 c 平面区域之间的表面间扩散较少，与 c 平面相比，这些小平面上 Ga 原子的掺入效率更高，可能导致形成富含 Ga 的条纹。我们使用平坦的 AlN/蓝宝石模板通过抛光证明了没有富 Ga 条纹的 AlGaN 生长；这导致在基于 AlGaN 的量子阱中实现了均匀的发射能量。我们使用平坦的 AlN/蓝宝石模板通过抛光证明了没有富 Ga 条纹的 AlGaN 生长；这导致在基于 AlGaN 的量子阱中实现了均匀的发射能量。我们使用平坦的 AlN/蓝宝石模板通过抛光证明了没有富 Ga 条纹的 AlGaN 生长；这导致在基于 AlGaN 的量子阱中实现了均匀的发射能量。