Basic Research of Ultra-Fine-Structure Fluoride/Si Light Emitting Device with Si Substrate

本项目是利用硅衬底实现超精细结构氟化物/硅发光器件的基础性研究，这通常被认为是很难应用于光电子集成电路(OEIC)的。主要目的是实现含氟(CaF_2)和硅的单晶超晶格或超精细周期结构，通过能带图分析建立该超晶格的材料性质理论，为该超晶格在光学器件中的应用提供基础知识。主要研究结果如下：利用电离团束外延(ICBE)技术研究了氟化物(CaF_2)-Si超晶格和超薄层的生长。明确了在Si(111)衬底上生长CaF_2薄层(-nm)和在CaF_2衬底上外延生长CaF_2薄层的条件。热力学上，由于每种材料的表面能差太大(…)，硅容易在CaF_2上团聚更大的。为了克服这一问题，我们研究了在相对较低的衬底温度600ﾟ下，电离和加速(Va=2KV)的生长过程。结果得到了50对5 nm-CaF_2/5 nm-Si超晶格，经原位反射高能电子衍射(RHEED)表征为单晶性质，扫描电子显微镜(SEM)观察到其表面较为平坦。采用紧束缚方法对CaF_2/Si超晶格的电子能带结构进行了理论分析，为CaF_2/Si超精细周期结构的光学性质奠定了理论基础。计算结果表明，随着硅层厚度的增加，CaF2/Si(100)超晶格的光学跃迁性质趋于直接跃迁，并且由于深绝缘层势垒量子阱对电子的限制，电子能级将显著量子化。通过这些结果，我们获得了超精细结构氟化物/硅发光器件的可能性和实现这些器件所必需的基本知识。较少

This project is a basic research for realization of ultra-fine-structure fluoride/Si light emitting device featured by using silicon substrate, which has usually been considered to by very difficult to apply to opto-electronics integrated circuit (OEIC). The main purpose is realization of single-crystalline superlattice or ultra-fine periodic structures with fluoride (CaF_2) and Si, establishment of the theory on material properties of this superlattice by analyzing energy band diagram in order to obtain basic knowledge on application of this superlattice to optical devices. Results obtained are summarized as follows.Crystal growth of fluoride (CaF_2) -Si superlattice and ultra-thin layers was investigated using ionized cluster beam epitaxy (ICBE). Condition of epitaxial growth of CaF_2 thin layers (-nm) on Si (111) layers, and Si layers on CaF_2 was made clear. Thermodynamically, Si tend to agglomerate on CaF_2 because the difference between the surface energy of each material is too … More large. To overcome this problem, we investigated the growth process at relatively low substrate temperature 600^ﾟ with ionization and acceleration (V_a=2KV). As a result, 50 pairs of 5nm-CaF_2/5nm-Si superlattice was obtained, which wafound to be single crystalline nature shown by in-situ reflection high energy electron diffraction (RHEED) and has relatively flat surface shown by SEM observation.Theoretical analysis was made for the electronic band structure of CaF_2/Si superlattice using tight binding method in order to establish the basis of the theory of optical properties of CaF_2/Si ultra-fine periodic structures. As a result of the calculation, it was found optical transition properties of the CaF_2/Si (100) superlattice approaches direct transition as the thickness of Si layer gets thinner, and that remarkable quantization of electron energy levels is expected due to electron confinement by deep insulator-barriered quantum wells.By these results, we obtained possibility of ultra-fine-structure fluoride/Si light emitting devices and basic knowledge essential to the realization of these devices. Less