Short Step-Bunching (SSB) are a kind of linear defects consisting of convex and concave undulations on the surface of 4H-SiC homoepitaxial layer. In this work, we report the characterizations of SSBs on 12 μm, 50 μm and 85 μm thick SiC epilayers by using optical microscopy (OM), micro-photoluminescence spectra (PL), atomic force microscopy (AFM), chemical mechanical polishing (CMP), molten KOH etching (10 min, 500 ℃) and high resolution transmission electron microscope (HRTEM). It is found that these SSBs are 200 ∼ 250 μm long, perpendicular to the step-flow direction, leading to local rugged surfaces of epilayer. No other poly-types are identified on and around these SSBs. H etching the substrate reveals the existence of short-line defects on the substrate with one or more dislocations (TSD or TED) or an amorphous bump locating in center of most of them. Presumably, the amorphous bump was a kind of carbon inclusion. Based on the above results, we proposed that the SSBs develop from the short-line defects generated when etching the substrates prior to epilayer growth. Elimination of short-line defects by proper etching process is an effective route to reducing the SSBs in 4H-SiC homoepitaxial layers.

中文翻译：

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4H-SiC同质外延厚膜短台阶聚束缺陷的表征及形成机制

短台阶聚束（SSB）是4H-SiC同质外延层表面由凸凹起伏组成的线状缺陷。在这项工作中，我们通过使用光学显微镜 (OM)、微光致发光光谱 (PL)、原子力显微镜 (AFM)、化学机械抛光 (CMP) 报告了 12 μm、50 μm 和 85 μm 厚的 SiC 外延层上的 SSB 的表征）、熔融KOH蚀刻（10分钟，500℃）和高分辨率透射电子显微镜（HRTEM）。研究发现，这些SSBs长200～250μm，垂直于阶跃流方向，导致外延层表面局部粗糙。在这些 SSB 上及其周围没有发现其他多型体。对衬底进行 H 蚀刻揭示了衬底上存在短线缺陷，其中有一个或多个位错（TSD 或 TED）或位于大多数位错中心的非晶凸块。据推测，非晶凸块是一种碳夹杂物。基于上述结果，我们提出SSB是由外延层生长之前蚀刻衬底时产生的短线缺陷产生的。通过适当的刻蚀工艺消除短线缺陷是减少4H-SiC同质外延层中SSB的有效途径。