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

本课题是利用硅衬底实现超精细结构氟硅发光器件的基础研究，该器件通常被认为很难应用于光电集成电路（OEIC）。其主要目的是用氟化物（CaF_2）和硅实现单晶超晶格或超细周期结构，并通过分析能带图建立该超晶格的材料性质理论，从而获得该超晶格在光学器件上应用的基本知识。所得结果总结如下。采用离子化簇束外延（ICBE）技术研究了氟化CaF_2 -Si超晶格和超薄层的晶体生长。明确了CaF_2薄层（-nm）在Si（111）层和Si层在CaF_2上外延生长的条件。在热力学上，由于两种材料的表面能差太大，Si倾向于在CaF_2上结块。为了克服这一问题，我们研究了在相对较低的衬底温度600^下电离和加速（V_a=2KV）的生长过程。得到50对5nm-CaF_2/5nm-Si超晶格，原位反射高能电子衍射（RHEED）显示其为单晶性质，SEM观察显示其表面相对平坦。采用紧密结合的方法对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理论奠定了基础。计算结果表明，随着Si层厚度的增加，CaF_2/Si（100）超晶格的光学跃迁性质接近于直接跃迁，并且由于深绝缘体势垒量子阱的电子约束，有望实现显著的电子能级量子化。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以及实现这些器件所必需的基本知识。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