Surface electron microscopy for understanding heteroepitaxy of GaP on silicon

在硅衬底上生长的晶格匹配的III-V半导体系统在高效多结太阳能电池以及将光电子学集成到硅技术中具有广阔的应用前景。然而，到目前为止，III-V外延层中的晶体缺陷阻碍了III-V/Si技术在工业应用方面的重大突破。利用各种补充电子显微镜方法，主要是LEEM，但也包括STM、SAM和SEM，本项目旨在量化和表征工业上相关的金属有机气相外延在单晶硅上生长的GaP层中的此类晶体缺陷。随着对原子尺度上缺陷形成的更好的理解，将制定避免缺陷的策略。在这个项目的第一阶段，我们已经建立了基本的方法来解释和很大程度上抑制GaP薄膜中反相无序的形成。这些基于特高压的方法将进一步发展和改进，以适应增长过程。为此，将在迄今尚未实现的与工艺相关的条件下进行电子显微镜研究。因此，可以在相应的前体压力下模拟生长过程，同时对表面进行显微镜成像。材料体系将扩展到与应用相关的含稀氮的GaP基多元体系。主要利用电子显微镜和反射各向异性谱来研究沉积材料在典型工艺条件下的结构和化学稳定性以及III-V/Si界面的成键结构。

Lattice-matched III-V semiconductor systems grown on Si substrates offer a promising potential for applications as high-efficiency multi-junctions solar cell as well as for integration of optoelectronics into Si technology. However, crystal defects in the III-V epi-layers have so far impeded a major breakthrough in industrial implementation of III-V/Si technology. Using a variety of complementary electron microscopy methods, mainly LEEM but also STM, SAM and SEM, this project aims at quantification and characterization of such crystal defects in GaP layers grown by industrially relevant metalorganic vapor phase epitaxy on single crystalline Si. With the resulting improved understanding of defect formation on the atomic scale, strategies to avoid defects will be developed. In the first period of this project, we have established basic approaches to explain and largely suppress the formation of antiphase disorder in the GaP films. These UHV-based approaches will be further developed and improved for adaption to the growth process. For this purpose, electron microscopy studies will be performed under hitherto unrealized process-related conditions. The growth process can thereby be emulated at relevant precursor pressures while imaging the surface microscopically. The material system will be extended to application-relevant dilute-N-containing GaP-based multinary systems. The structural and chemical stability of the deposited materials under typical processing conditions and the bonding structure at the III-V/Si interface will be addressed utilizing mainly electron microscopy and reflection anisotropy spectroscopy.