de Matteis Diego, De Luca Marta, Fadaly Elham M T, Verheijen Marcel A, López-Suárez Miquel, Rurali Riccardo, Bakkers Erik P A M, Zardo Ilaria
Departement Physik, Universität Basel, 4056 Basel, Switzerland.
Department of Applied Physics, Eindhoven University of Technology, 5612AP Eindhoven, The Netherlands.
ACS Nano. 2020 Jun 23;14(6):6845-6856. doi: 10.1021/acsnano.0c00762. Epub 2020 May 18.
Recent advances in nanowire synthesis have enabled the realization of crystal phases that in bulk are attainable only under extreme conditions, .., high temperature and/or high pressure. For group IV semiconductors this means access to hexagonal-phase SiGe nanostructures (with a 2H type of symmetry), which are predicted to have a direct band gap for up to 0.5-0.6 and would allow the realization of easily processable optoelectronic devices. Exploiting the quasi-perfect lattice matching between GaAs and Ge, we synthesized hexagonal-phase GaAs-Ge and GaAs-SiGe core-shell nanowires with up to 0.59. By combining position-, polarization-, and excitation wavelength-dependent μ-Raman spectroscopy studies with first-principles calculations, we explore the full lattice dynamics of these materials. In particular, by obtaining frequency-composition calibration curves for the phonon modes, investigating the dependence of the phononic modes on the position along the nanowire, and exploiting resonant Raman conditions to unveil the coupling between lattice vibrations and electronic transitions, we lay the grounds for a deep understanding of the phononic properties of 2H-SiGe nanostructured alloys and of their relationship with crystal quality, chemical composition, and electronic band structure.
纳米线合成技术的最新进展使得实现一些晶体相成为可能，这些晶体相在体相中只有在极端条件下，如高温和/或高压下才能获得。对于IV族半导体来说，这意味着可以制备六方相SiGe纳米结构（具有2H型对称性），据预测其直接带隙可达0.5 - 0.6，这将有助于实现易于加工的光电器件。利用GaAs和Ge之间近乎完美的晶格匹配，我们合成了六方相GaAs - Ge和GaAs - SiGe核壳纳米线，其[此处原文似乎缺失关键信息]高达0.59。通过将位置、偏振和激发波长相关的μ - 拉曼光谱研究与第一性原理计算相结合，我们探索了这些材料的完整晶格动力学。特别是，通过获得声子模式的频率 - 成分校准曲线，研究声子模式沿纳米线位置的依赖性，并利用共振拉曼条件揭示晶格振动与电子跃迁之间的耦合，我们为深入理解2H - SiGe纳米结构合金的声子特性及其与晶体质量、化学成分和电子能带结构的关系奠定了基础。
