Fundamental Study of GaN-on-Si Hetero-Epitaxial Substrate for Earth Environmental Preservation

氮化镓及其化合物是高功率器件和紫外波长区域光电器件的唯一有前途的材料。许多基于氮化镓的光电器件在蓝宝石和碳化硅衬底上进行了演示。另一方面，尽管硅具有质量高、成本低、电导率可控以及与Si- ulsi技术相结合应用的有效性等诸多优点，但基于硅衬底的氮化镓器件尚未得到应用。由于氮化镓层与硅衬底之间的异质界面容易发生相互作用，因此很难在硅衬底上获得高质量的氮化镓薄膜。因此，期望使用适当的缓冲层在Si上生长器件质量的GaN涂层。本文采用原位反射高能电子衍射系统，采用NH3气源分子束外延技术，在Si（111）和Si（100）衬底上覆盖0.6μm厚的γ-Al_2O_3外延层作为中间层，研究了GaN外延层的生长行为。结果表明，γ- al_2o_3层有效抑制了Si衬底表面的氮化。在γ-Al_2O_3Si（100）衬底和γ-Al_2O_3Si（100）表面平坦的六角形GaN层上外延生长立方相GaN。

The GaN and compounds of AlGaN are only promising materials for high-power devices and opto-electronic devices in the ultra violet-wavelength region. Many GaN-based opto-electronic devices are demonstrated on sapphire and SiC substrate. On the other hand, the GaN-based devices on silicon substrate have not been performed regardless of many advantages of Si such as high quality, low cost, controllability of the conductivity and effectiveness for the application combined with Si-ULSI technology. It is hard to obtain high quality GaN epilayer on Si because it is easy to occur the interaction at the hetero-interface between GaN layer and Si substrate. Therfore, it has been expected to grow a device-quality GaN epilayer on Si using an appropriate buffer layer.In the present work, we have investigated the growth behavior of GaN epilayer on Si(111) and Si(100)substrates coverd with 0.6μm thick γ-Al_2O_3 epitaxial layer as an intermediate layer by NH3 gas source molecular beam epitaxy with in-situ reflection high energy electron diffraction system. It is found that the nitridation of the surface of the Si substrate is effectively suppressed with γ-Al_2O_3layer. The GaN under cubic phase was epitaxially re-grown on γ-Al_2O_3Si(100) substrate and hexagonal GaN layer with flat surface on γ-Al_2O_3Si(100)