Powell Kaden M, Yoon Heayoung P
Electrical and Computer Engineering, University of Utah, Salt Lake City, UT, 84112, USA.
Materials Science and Engineering, University of Utah, Salt Lake City, UT, 84112, USA.
Appl Microsc. 2020 Sep 3;50(1):17. doi: 10.1186/s42649-020-00037-4.
Recent advances in fabrication have enabled radial-junction architectures for cost-effective and high-performance optoelectronic devices. Unlike a planar PN junction, a radial-junction geometry maximizes the optical interaction in the three-dimensional (3D) structures, while effectively extracting the generated carriers via the conformal PN junction. In this paper, we report characterizations of radial PN junctions that consist of p-type Si micropillars created by deep reactive-ion etching (DRIE) and an n-type layer formed by phosphorus gas diffusion. We use electron-beam induced current (EBIC) microscopy to access the 3D junction profile from the sidewall of the pillars. Our EBIC images reveal uniform PN junctions conformally constructed on the 3D pillar array. Based on Monte-Carlo simulations and EBIC modeling, we estimate local carrier separation/collection efficiency that reflects the quality of the PN junction. We find the EBIC efficiency of the pillar array increases with the incident electron beam energy, consistent with the EBIC behaviors observed in a high-quality planar PN junction. The magnitude of the EBIC efficiency of our pillar array is about 70% at 10 kV, slightly lower than that of the planar device (≈ 81%). We suggest that this reduction could be attributed to the unpassivated pillar surface and the unintended recombination centers in the pillar cores introduced during the DRIE processes. Our results support that the depth-dependent EBIC approach is ideally suitable for evaluating PN junctions formed on micro/nanostructured semiconductors with various geometry.
制造技术的最新进展使得径向结架构可用于具有成本效益的高性能光电器件。与平面PN结不同，径向结几何结构在三维（3D）结构中最大化了光学相互作用，同时通过共形PN结有效地提取产生的载流子。在本文中，我们报告了由深反应离子刻蚀（DRIE）制造的p型硅微柱和通过磷气体扩散形成的n型层组成的径向PN结的特性。我们使用电子束诱导电流（EBIC）显微镜从柱体的侧壁获取3D结轮廓。我们的EBIC图像揭示了在3D柱阵列上共形构建的均匀PN结。基于蒙特卡罗模拟和EBIC建模，我们估计了反映PN结质量的局部载流子分离/收集效率。我们发现柱阵列的EBIC效率随入射电子束能量的增加而增加，这与在高质量平面PN结中观察到的EBIC行为一致。我们的柱阵列在10 kV时的EBIC效率约为70%，略低于平面器件（≈81%）。我们认为这种降低可能归因于未钝化的柱表面以及在DRIE过程中引入的柱芯中意外的复合中心。我们的结果支持深度相关的EBIC方法非常适合评估在具有各种几何形状的微/纳米结构半导体上形成的PN结。
